The correct answer is B) unbalanced rudders. Most lifeboats are equipped with unbalanced rudders, which means the rudder post is not centered on the rudder. This design provides better control and maneuverability of the lifeboat, especially at low speeds, which is crucial for emergency situations. Unbalanced rudders require less force to turn the boat compared to balanced rudders, making them the preferred choice for lifeboats. The other options are incorrect because balanced rudders are more common in larger vessels, contraguide rudders are a specialized design rarely used in lifeboats, and straight rudders would not provide the necessary maneuverability required for a lifeboat.