What is this? Please answer with an explanation

It's C.

Explanation:

The process of nitrification is that is a process that converts ammonia to nitrite and nitrite to nitrate. It is an important step in the global nitrogen cycle. It is exclusively carried out by prokaryotes, which is a group of organisms called bacteria.

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the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

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