a. Yes, because of the self-reference effect; regardless of how he answered, your brother would probably remember the word better after associating it with himself.
b. Yes, because of the self-reference effect—but ONLY IF he answered that he was conniving. His memory for the word would only be enhanced if he actually did think of himself as (at least sometimes) conniving.
c. No, even if he did answer that he was conniving. The self-reference effect typically works only with positive words (and not with negative words) since most people are driven by the self-enhancement motive.
d. No, even if he did answer that he was conniving. In fact, thinking about the self tends to be distracting, and would most likely make your brother LESS likely to remember the word.