For the carbon cycle and the nitrogen cycle to function properly, which organisms must always be present?
a) decomposers
b) herbivores
c) parasites
d) predators

I think the answer is "A"

Explanation:

The hint said very small. Mushrooms. There normally small. And they are decomposers. Plus, Decomposers are necessary to keep nitrogen and carbon moving through the cycle, and not locked up in the atmosphere or in other organisms.

d.

explanation:

supercell thunderstorms are perhaps the most violent of all thunderstorm types, and are capable of producing damaging winds, large hail, and weak-to-violent tornadoes