You Said:

B. First he rearranged, then proposed, and lastly experimented to get his answer.

It’s a common practice when stuck or feeling hopeless to start “rearranging” things hoping an answer will leap out at you. And while this reshuffle and deal ‘em again approach might work well in card games and certain attempts to get divine guidance, this student noticed that the letters in the multiplicand were in order (s-z). Seeing this pattern, “rearranging” as a first action would be considered totally random, an act of panic and desperation. Choose an answer where the student employed an activity that enabled him to discover the identity of the multiplier.