Part A

Select the correct statement describing the nitrogen cycle.

Denitrifying bacteria reduce ammonia $(N{H}_3^{+})$to molecular nitrogen $(N_2).$

Nitrogen$-$fixing microbes provide energy for carbon fixation.

Bacteria obtain energy from nitrification.

Biological magnification means that

the concentration of toxins increases at higher trophic levels in a food chain

large species play a more important role in communities than small species

fat$-$soluble toxins magnify the effects of other toxic materials