Answer:
The second one: You are, if I'm not mistaken, a good person for this experiment.
Explanation:
The first sentence, "You are, if I'm not mistaken a good person, for this experiment." does not have a comma after "mistaken", where there should be one. After "a good person", there should not be a comma.
<span>Science fiction is sometimes divided into "hard" and "soft" science fiction.</span>
whom
Explanation:
the lady to whom you spoke just now is my teacher