The correct answer is B) apply left rudder. When your starboard engine stalls while going ahead on twin engines with the rudder amidships, applying left rudder will help maintain your course. This is because the loss of thrust on the starboard side will cause the boat to yaw to the right. Applying left rudder counteracts this yaw and keeps the boat going straight. The other options are incorrect because: A) keeping the rudder amidships will not compensate for the loss of thrust, D) applying right rudder will exacerbate the yaw to the right, and C) increasing engine speed on the port engine alone will not be enough to overcome the starboard engine stall.