The right answer is "A. Warmth and comfort"
First, in the context of language, the simile is considered the figure of explicit comparison - since there are other types that also compare, such as metaphor and analogy, for example. However, simile presents itself as a more objective resource, and for that, what characterizes it and differs from others is the use of connectives to highlight the comparison being made. In the case of the sentence exposed in the question the connective is "like".
Second, the author of the phrase "like a pair of thick socks / the cold can not bite through." is comparing something or someone with the sensation that thick socks provide in cold situations, which is comfort and a warm feeling in the feet.
