The correct answer is C) Gravity. Gravity davits are the type that may be operated by one person. This is because gravity davits use the weight of the lifeboat or life raft to lower it into the water, rather than requiring mechanical lifting force. The weight of the craft causes the davit to lower it gradually and safely with minimal effort from the operator. In contrast, the other davit types listed (radial, sheath-screw, and quadrantal) typically require more force and coordination from multiple crew members to operate effectively and safely.