My 2 cents below, I tried to think through the other ones:
A. Yes, because an amino acid change has occurred.
(A gene mutation occurred, not an amino acid change)
B. Yes, because all mutations change the resulting protein.
(Sounds correct. Gene -> mRNA -> protein)
C. No, because the amino acid sequence has not been changed.
(The gene mutation means the amino acid sequence <em>has</em> changed)
D. No, because mutations in the DNA do not affect the mRNA sequence.
(They do so)