Nitrogen fixation
a. is the process where nitrogen is converted to a usable form
b. is accomplished by plants when they break down soil
c. occurs as a result of photosynthesis
d. none of the above

Nitrogen fixation .

b. is accomplished by plants when they break down soil

Explanation:

To understand this answer we have to analyze the options. First of all, a is incorrect because without nitrogen fixation nitrogen can be used. Nevertheless, it is the only process that makes nitrogen usable for plants or microorganisms, but the statement lacks information to be the truth.

c. is incorrect because nitrogen fixation is carried out before the photosynthesis process. Not after and as a cause of it.

d. is wrong because it is part of the soil break down process.

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