The correct answer is D) the effects of buoyancy removing the weight of the raft from the hook. When a davit-launched raft becomes waterborne, the raft's weight is supported by the buoyancy of the water, rather than the hook. This causes the weight of the raft to be removed from the hook, allowing the hook to release the raft automatically without any additional action required. The other options are incorrect because they describe actions that are not necessary for the automatic release of the raft. Releasing the boarding flap and bowsing lines (A), activating a release lock (B), or pulling a lanyard (C) are not the mechanisms that cause the raft to be released upon becoming waterborne.