Which question can be answered by an experiement

They forgot the answers

A. Do sugar substitutes cause cancer

B. Did an ice age kill off the mastodons

C. What caused the extinction of the dinosaurs

D. Are all people susceptible to the hunta virus

I say both A and D can be answered with and experiment.

do yall know the answer?

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.