Hundreds of years ago, sailors used to use constellations to navigate their ships at night.

The color of human skin is determined by a substance called melanin. What does the word DETERMINED mean in this sentence?

Hibernation is when an animal becomes inactive, or sleeps, during the short, cold days of winter. What does INACTIVE mean?

Gorillas use gestures, body language, facial expressions, sounds, chest slaps, and drumming to communicate what they are thinking. What is a GESTURE?

Tropical rainforests are very dense forests that are full of trees. What does DENSE mean?

Rainforests help the Earth's climate by absorbing carbon dioxide. What does ABSORB mean?

Did you know that popsicles were invented by accident? In 1905, an eleven year old boy named Frank Epperson who lived in San Francisco unintentionally invented them. What does UNINTENTIONALLY mean?

Cats also have flexible backbones and no collarbone. This is important because it reduces the amount of damage cats get when they fall from something tall. What does REDUCE mean?

Walking on the moon was a significant moment in history for many Americans because no other person or country had landed on the moon prior to this event. What does SIGNIFICANT mean?

He has numerous rocks in his collection. He has been collecting rocks since he was 4! What does NUMEROUS mean?

The old wooden building started to collapse after the heavy storm weakened its walls. What does COLLAPSE mean?

The Earth is tilted because of a giant collision 4.5 billion years ago. A Mars-sized object is thought to have crashed into young Earth. What is a COLLISION?