Wrong answer, Rookie!

A, B, and D are wrong. The contact is on the far side of the convoy from your position. You cannot even be certain that there actually is a u-boat. You also can't tell if there are other u-boats in the area. This is not the right time to take rash actions. Do not abandon your position - the real danger might be on your side. Tightening up the convoy may be unnecessary and it gives the u-boats more targets in less area. Making a smoke screen may alert every u-boat in the area to your position.
The best response is "C" to hold your position and get ready for action stations.