Animals get the most of the nitrogen they need a
by consuming plants or other animals.
b
by breathing in atmospheric nitrogen.
c
directly from bacteria in the soil.
d
from the process of denitrification.

a

by consuming plants or other animals.

Explanation:

Animals get the nitrogen they need by eating plants or other animals that contain nitrogen.

A

Explanation:

Animals get the nitrogen they need by eating plants or other animals that contain nitrogen.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

correct answer is a. and d.