Aresearcher tests the hypothesis that large, daily doses of vitamin c protect against catching the common cold. what would be the best experimental and control group to test this hypothesis?

The best thing to do is this: 
the subjects in the experimental group should be given large, daily dose of vitamin C while the control group subjects should be given a daily dose of sugar pills that are disguised as vitamin C.
The research can then observe the differences between the two groups.

I’m not exactly sure what your trying to ask, but if it’s how an organelle is similar to a body system or a part a nucleus is like a in function. but i don’t fully understand what you’re trying to ask