Question

Why is the nitrogen cycle considered a closed system?

A.
because nitrogen is fixed by bacteria and assimilated by plants
B.
because nitrogen neither enters nor leaves the system
C.
because nitrogen is converted into nitrates and ammonia
D.
because nitrogen is created by bacteria and destroyed by plants

Answer 1

B

Step-by-step explanation:

I did it and it is B

Answer 2

B nitrogen stays in order so it can't change movement