After several miles of running and sprinting in intervals, the runner’s muscles ache and feel fatigued. which is the best explanation for what has occurred?

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

the answer to your question is sperm