This reaction is an example of a substitution reaction in which methoxy group (OCH₃) reacts with HI (hydroiodic acid). The bond between carbon and oxygen in the methoxy group breaks, leading to the formation of methanol (CH₃OH) and methyl iodide (CH₃ - I) as products. The correct reaction is:
\[
CH₃ - C - OCH₃ + HI \to CH₃OH + CH₃ - I
\]
Thus, A = CH₃OH and B = CH₃ - I.