He stumbled at the stone and fell . . . . . . . . a ditch.

The correct answer is B. into.

The word “into” is used to indicate movement from one place to another. In this case, the man is moving from the ground to the ditch. The other options are not as accurate because they do not indicate movement.

• On indicates that something is located on top of something else. In this case, the man is not located on top of the ditch.
• In can be used to indicate movement into a place or to indicate that something is located inside a place. In this case, the man is moving into the ditch, so “in” is a more accurate option than “on.”
• Within can be used to indicate that something is located inside a place or to indicate that something is included in a group. In this case, the man is not located inside the ditch, so “within” is not an accurate option.