1. Reaction
   Power source
2. Inaction
   Nothingness

It’s one of the basic laws of the universe: Any action will have a reaction equal and opposite to it. This is why jet engines can make planes fly, for example.

1. Gold
   Sulfur
2. Nitrogen
   Hydrogen

Hydrogen is the most common element in the universe. It’s highly flammable, while at the same time is a component of water. It's also very light.

1. Humans
   Evolution
2. A new volcano
   Soil erosion

Charles Darwin observed how some animals on Galapagos had adapted to the local area, separate from those in other islands. This process of animals developing to adapt to their environment is now known as evolution.

1. Positive
   Negative
2. The middle side
   No side

The positive and negative sides of a magnet attract the opposing sides of other magnets. Some magnets are so strong when they attract each other that you can injure yourself if your hand is caught between them!

1. Toes
   Ankles
2. Ears
   Wrist

The smallest bone in the body is known as the stirrup bone, which is actually located inside our ears. It’s part of our hearing mechanism, and it’s only about a tenth of an inch long.

1. Gold
   Salt
2. Wood
   Quartz

Technically speaking, a mineral is made up of crystals formed under the ground due to pressure, heat, and other factors. In many cases, mineral deposits are a mix of many different elements. Therefore, wood cannot be considered as a mineral by this definition.

1. Reed Bank
   Florida Reef
2. Great Barrier Reef
   Red Sea Reef

The Great Barrier Reef is the biggest reef system in the world, and it is located near the coast of Australia, well within the country’s territory. A reef is a big undersea community based on coral, organisms that grow large stone-like structures as their “shells.”

1. Flooding
   Strong winds
2. Lightning strike
   Flying objects

Electricity tends to find the shortest way from one place to another. If you’re the tallest object in an open field during a storm, you’re the lightning rod, therefore it will strike you. It’s the same reason you should avoid tall trees when outside, because the lightning will find them and strike, which could hurt you in the process.

1. It has dark soil there
   We never see that side
2. It's near the shadowy edges
   It has the remains of a civilization there

The time it takes for the moon to orbit around the Earth is about the same time it takes to spin around its own axis. That means the moon always shows us the same side all the time. The outer side is therefore dubbed as the “dark side” because we never see it facing the earth.

1. Yes
   No
2. Studies are still ongoing
   Still looking for archaeological proof

Scientists have found that theropod dinosaurs, which include the Tyrannosaurus Rex, are actually the ancestors of birds. In fact, some dinosaur fossils have evidence of feathers! That’s how evolution works.

1. Sun and moon are beside each other
   The sun rises and sets together with the moon
2. Moon is in front of the sun
   Sun naturally dims for a while

A solar eclipse happens if the moon comes between the earth and sun, so the moon blocks the sun’s light. On the other hand, a lunar eclipse happens if the earth blocks the light from hitting the moon.

1. Cotton gin
   Telephone
2. Radio
   Camera

Bell invented the telephone, while working with a mechanic named Thomas Watson. His invention changed the world of mass communication, as his invention is still being reinvented anew in the digital era.

1. Cirrus
   Nimbus
2. Stratus
   All of the above

Clouds are categorized by types, each with a distinct look and appearance in the sky. Cirrus are generally thin and rather wispy, cumulous are the very curly and puffy ones, nimbus are the dark ones that are actually rainclouds, and stratus are that stretch of clouds that simulate a thick blanket, kinda like a fog in appearance.

1. Yes
   No
2. Depends on the reflecting surface
   Depends on the time of day

White light is not a true color in the sense of how we perceive the other colors of the spectrum. White light is all the other colors combined.

1. Yes
   No
2. They're still debating about it
   Saturn has no rings anymore!

Saturn may have the largest and most visible rings, but it turns out that Uranus, Neptune, and Jupiter all have rings, too. Many scientists believe that rings are made from the leftovers of moon formation, and continuous explorations give us newer findings like these over the years.

1. Oil
   Tap water
2. Milk
   Wine

Louis Pasteur invented pasteurization, a process by which milk had most, if not all harmful organisms, removed. In short, he made milk safe to drink, and also gave it the ability to be preserved for a longer time.

1. Veggie
   Fruit
2. Both
   Neither

Surprisingly, the cool cucumber is not considered as a vegetable, and neither is it considered a fruit. Technically, it’s a member of the melon family of edible plants.

1. Plane has powerful engines
   Plane has jet engines
2. Plane is at maximum speed
   Plane is flying faster than sound

Sonic booms are created when a plane flies faster than the speed of sound, which is about 767 miles per hour. It’s made by air pressure shockwaves that are formed as a plane flies fast, with the shockwaves turning into a “cone” behind it.

1. Yes
   No
2. Only when it occurs at night
   Only when cooled

Magma is what we call the molten rock underneath the earth. However, once it comes out of a volcano, it’s automatically called lava.

1. Prime Meridian
   Rose line
2. Equator
   Grid

The equator is that line that horizontally divides the earth into the Northern Hemisphere and the Southern Hemisphere. There are several countries that the equator touches upon, but it's closest to Ecuador in South America, and they have a monument that marks it.

1. Shape of the beach
   Volcanic action
2. The moon
   Wind

The moon’s orbit around the earth creates the tides in the earth’s bodies of water. That’s because the moon’s gravity can pull at bodies of water when it moves.

1. When water wears down mountains
   Creation of instant islands and continents
2. When earth moves
   It’s just a theoretical construct

Continental drift describes how continents are moving around. Many scientists believe there was one supercontinent in ancient times, then geologic movement broke it up to the continents and islands we know today.

1. Johannes Kepler
   Carl Sagan
2. Stephen Hawking
   Galileo Galilei

Stephen Hawking discussed black holes at length in his books and his work. He was able to work on his theories, even though he was effectively paralyzed for majority of his life.

1. Sir Isaac Newton
   Elizabeth Blackwell
2. Robert Boyle
   Tycho Brahe

Sir Isaac Newton changed a lot of scientific notions during his lifetime, since he established many laws that are cited up to now. The discovery of gravity is also attributed to him, now referred to as Newton's law of universal gravitation. Generally, he had a huge contribution in the scientific field of physics.

1. Rivers
   Oceans
2. Lakes
   Waterfalls

The great human construction project known as the Panama Canal links together the huge Pacific Ocean and the Atlantic Ocean. It has many segments where water levels are raised or lowered, so boats can pass through safely.

1. Hydrogen
   Oxygen
2. Sodium
   Carbon

Our planet’s surface has a lot of the element called oxygen. About half of our planet’s crust, waters, and atmosphere is made up of oxygen, and the human body contains it, too.

1. Mercury
   Venus
2. Earth
   Mars

Although Mercury is closer to the sun, Venus is still the hottest planet in the solar system. That’s because the planet’s atmosphere traps heat, making the surface very hot, around 864 degrees Fahrenheit, or 462 degrees Celsius.

1. The mouse
   The fly
2. The house lizard
   The ant

Flies seem like harmless creatures, but their feet land on junk, feces, and food alike. This makes them pass on deadly sicknesses with their “footsteps.” That’s why it’s always a smart move to swat them away before they land on your food or your kitchenware, or anywhere near you.

1. Gregor Mendel
   Alessandro Volta
2. Thomas Alva Edison
   Alfred Nobel

Thomas Alva Edison patented many inventions in his lifetime, and a lot of them became great technology we still use today. The lightbulb is one of his most significant contributions to society.

1. Alloy
   Steel
2. Rust
   Fool's gold

Iron oxide is the chemical term for the very common problem known as rust. When iron is exposed to air, oxygen bonds with iron atoms to make iron oxide, which is a much weaker material. Needless to say, it’s a formula that doesn’t work well with our tools.

1. Marrow cells
   Blood cells
2. Brain cells
   Lung cells

Your brain cells will be around from the time you’re a baby until you grow old and die. On the flip side, some parts of the brain do not replace brain cells when they die, so you have to be careful of how you treat them on a daily basis.

1. Silver
   Arsenic
2. Radium
   Cobalt

There are many female scientists out there, but perhaps one of the most well-known is Marie Curie, who worked with fellow scientist and hubby Pierre Curie, and continued working on scientific knowledge even after his death. She also discovered polonium, and won the Nobel Prize for both physics and chemistry for her work, then also did work that contributed to the development of the x-ray.

1. Yes
   No
2. Depends on their environment
   Only if they feel sick

Snakes are one of the truly meat-eating animal species in the world. They do not eat any kind of plant at all, unless their prey ate plants. They are that carnivorous.

1. Frogs
   Snakes
2. Jellyfish
   Mushrooms

Some indigenous tribes in South America coat their darts with poison taken from frogs. Poisonous frogs tend to be very colorful, and there are various species of them in that continent, especially in the Amazon Rainforest where specific species of poisonous frogs are exclusively found.

1. Parmesan
   Sugar syrup
2. Salt
   Water

Sodium is Na and chloride is Cl, which forms the chemical compound of NaCl or sodium chloride, which we also know as salt. Sodium is considered as an essential mineral that the human body actually needs to perform several functions, so it's nice to have salt in your diet, just not too much of it.