Bacteria in soil convert atmospheric nitrogen into a form usable by plants.
Bacteria are single-celled organisms.
Single-celled organisms in soil convert atmospheric nitrogen into a form usable by plants.
What in soil converts atmospheric nitrogen into a form usable by plants?

a: compound of hydrogen oxygen
b: carbohydrates
c: single-celled organisms
d: excretory structures
e: peachleaf willow
f: members of their own species
g: It helps them survive
h: deoxyribonucleic acid