The first forms of life on earth were
a. plants
b. microorganisms
c. birds
d. dinosaurs 5. a suggested and testable explanation for an event is called a
a. hypothesis
b. variab

The first form of life were b. microorganisms :)

For question 5, the answer should be a. Hypothesis

Air occupies

There are four nitrogenous bases that make up dna. the two pyramidines are thymine and cytosine. the two purines are adenine and guanine. these bases pair in a very specific way. adenine - thymineguanine - cytosine i remember it like this: a tall, good cat.