What is the second most abundant element on earth and seems to be very important in biological processes such as oxygen transportation in the body and cellular respiration

iron

Explanation:

Cellular respiration may be defined as the group of metabolic processes as well as reactions which occurs in the cells of the organisms that converts the chemical energy from the oxygen molecules or from nutrients into ATP or adenosine triphosphate and then releases the waste products. Thus it breaks the glucose and produces the ATP. Iron is an important element which are used in many important biological processes in the body like the cellular respiration and oxygen transportation.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.

it's not c. i took the quiz and got it wrong. so my best guess is b.

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