Before there was life on earth, which gas was absent from the ancient atmosphere?

a. ammonia
b. methane
c .nitrogen
d. oxygen

Name one similarity and one difference between the morphology of a brachiopod and a bivalve

What is a sex-linked genetic disorder that disrupts the blood's ability to clot? a. achondroplasia b. huntington's disease c. hemophilia d. albinism

In the practice of science, this type of reasoning is used to develop explanations.