You Said:

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

To those who like to “look before they leap,” it seems logical to start with proposing before taking action. Unfortunately, many of us look and look, but never leap, or by the time we do, someone else has grabbed the prize. This student, though, had a bias for doing something. Choose an answer where the student employed an action that enabled him to discover the identity of the number in the one’s place.