Answer: False
Explanation:
Protozoans are not the organism that fix nitrogen for the plants. The organism that fix nitrogen to convert it into a form which can be used by plants are known as diazotrophs.
These are bacteria and archae that fix nitrogen gas found in the atmosphere into more usable form such as ammonia.
These organism can grow without any external source of fixed nitrogen. Example: Rhizobia and azospirillium.
He could race multiple cars with different weight added on them and do multiple races (just to be sure) and see if his theory was correct, if not he should right down what he has learned from his experience! :D
-You'll never learn if u don't try ;)