Which component provides stability and structural integrity at the rear of a boat?

The transom is the correct answer because it serves as the rear structural support of a boat, providing stability and strength to the entire hull. It is the vertical part at the back of the boat that connects the sides of the hull and supports various components, like the motor or outboard engine. The transom is crucial for ensuring that the boat maintains its shape and integrity while navigating through water, especially under the pressures exerted by waves or the weight of the motor.

The other components play different roles: the stern drive is a type of propulsion system that combines the features of an inboard and outboard motor. The drive shaft transmits power from the engine to the propulsion system but does not provide structural support. The impeller is part of the water pump system and helps in circulating coolant or propulsion in jet drive systems, but again, it does not contribute to the stability or structural integrity of the boat's rear.