What is the main way that active transport differs from diffusion?

Active transport is different from diffusion because it requires energy expenditure, while diffusion requires no energy at all. In diffusion, materials are moving from areas of high concentration across the cell membrane into areas of low concentration. This requires no energy on the part of the cell. In active transport, however, the cell is moving material between two areas of equal concentration, or from an area of low concentration into an area of high concentration. This requires the cell to expend energy.

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.

correct answer is a. and d.