Why are bacteria a necessary part of the nitrogen cycle?

 Bacteria are necessary because they are doing the very important processes for the nitrogen cycle like as ammonification, nitrogen fixation, and nitrification. 
As Nitrogen cannot be used in its form because of its chemical form so it is changed to various forms in the nitrogen cycle, bacteria has a big help in the process.

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).

Telophase colchicine is a chemical obtained from plants that prevents the assembly of spindle fibers