Comment by stared
Well, "Is {sentence_a} similar to {sentence_b}?" is the correct query when we care about some vague similarity of statements. In this case, we should go with something in the line "Is {answer} a plausible answer to the question {question}".
In any way, I see how the example "Is {sentence_a} similar to {sentence_b}?" breaks the flow. The original example was:
{question}
# A
{sentence_A}
# B
{sentence_B}