What converts nitrogen into a usable substance during the nitrogen cycle?

a. consumers
b. decomposers
c. leaches
d. nitrogen fixing bacteria

D.Nitrogen fixing bacteria

Explanation:

Fertile soil contains combined nitrogen, mainly in the form of nitrates, nitrites, ammonium or urea salts, CO (NH2) 2. These compounds are absorbed from soil water by plant roots in a process known as nitrogen fixation. A few species of bacteria and cyanobacteria can "fix" atmospheric nitrogen, that is, transform N2 gas into nitrogen compounds; nitrates or ammonium salts. These bacteria can be called nitrogen-fixing bacteria.

The most important genus of these bacteria is Rhizobium. They live in symbiosis in the root nodules of plants of the legume family, for example, peas, beans, clover and alder. Other nitrifying bacteria live free in the soil, for example aerobic bacteria such as Azobacter and Beijerinckia, and anaerobic bacteria such as Clostridium pastorianum. These bacteria require small amounts of certain transition metals like molybdenum, iron, cobalt and copper, as well as boron from the soil.

atp is used for energy.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.