What process makes nitrogen useful to crops? a)nitrogen compounding b)nitrogen conversion c)nitrogen fixation d)nitrogen reaction

D.) nitrogen fixation

Explanation:

Nitrogen is in the soil and helps plants grow.  This process is nitrogen fixation.

C) nitrogen fixation

Explanation:

Nitrogen fixation is the process by which atmospheric nitrogen is fixed in the soil  by the soil bacteria. The nitrogen is present in the atmosphere but cannot be used by the plants directly in the inorganic form thus the soil bacteria convert the atmospheric nitrogen into other forms such as nitrates and ammonia. The plants absorb these forms through their roots and in return the bacteria receives the nourishment. The nitrogen is essential for the growth of the crops in the sense it is an important ingredient of aminoacids which is required for the production of proteins, and nucleic acids.

d. the weight of the book