The phrase from the excerpt that suggests that Krogstad is prone to engage in crime and may, in fact, be a criminal is the following one:
diseased moral character
It is the only option that talks about somebody being a bad person, which is what Krogstad is. The other options do not show that moral ambiguity this option does.
C from the randomness of self determination
It is false. The sentence should be: The colors in the painting appear particularly vibrant in this light.
Christopher McCandless was detaching, separating from society, he bonded with people but he didn't want to feel attached. He tells Ronald Franz that they will talk about it when he, Chris, comes back from Alaska. He didn't refused openly to the idea, but didn't commit either.
