How does the effect known as "bank suction" act on a single-screw vessel proceeding along a narrow channel?

Correct Answer: Option B — It pulls the stern toward the bank.

Bank suction occurs because the water level between the stern and the bank drops due to the propeller's suction. This creates a low-pressure area that pulls the stern toward the bank, which can lead to a dangerous situation where the vessel loses directional control and potentially grounds.