Nitrogen fixation is carried out by?
A. Plants
B. Animals
C. Humans
D. bacteria

Mike has a problem with his testosterone. he is unable to produce enough. which will most likely be affected by his inability to produce testosterone? check all that apply.

For a comparative or experimental investigation, scientists often make a testable about a scientific question, and then they test it in the investigation. a.control b.hypothesis c.procedure d.system

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?