question:
Which human organ system exchanges gases with the environment?

answer:
respiratory

question:
Which is an example of a chemical reaction?

answer:
The burning of wood

question:
The best evidence that two land areas were once connected is the discovery that both land masses

answer:
have similar types of rocks and fossils.

question:
A boy pulls a sweater off over his head. His hair is attracted to the sweater due to

answer:

an electrical charge