Which statement about life on earth is true? a. dinosaurs appeared before insects.
b. dinosaurs and insects appeared at the same time.
c. humans have been on earth for hundreds of millions of years.
d. humans have been on earth for a very short sling of time.

c.hu!and have been on Earth for hundreds of years

Explanation:

just feels right

that is a club

explanation:

i am good at it i think hope its right

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.