The correct answer is A) help to prevent broaching. When a sea anchor is properly rigged on a survival craft, it helps to prevent the craft from broaching, which is when the craft turns sideways to the waves, exposing it to potential swamping or capsizing. The sea anchor creates drag and helps to keep the craft's bow pointed into the waves, improving stability and reducing the risk of broaching. The other answer choices are incorrect because: B) a sea anchor does not completely stop the survival craft from drifting, it just reduces the drift rate; C) the sea anchor does not prevent the craft from rolling, it helps stabilize the craft; and D) the sea anchor does not prevent pitching, which is the up-and-down motion of the bow and stern.