Choice "D" - telling your friend to stay silent and waiting until dark to rescue him - sounds cruel. He's going to be out there all day in pain, likely bleeding. However, any movement in No Mans Land during daylight can get you killed. There's always snipers just waiting for a target, plus if an enemy spotter sees movement, the Germans will open up with machine guns, rifles, and mortar fire. The only answer that makes sense is "D", waiting until dark to help your friend.

Going out there yourself just means there will be two wounded men trapped in No Mans Land. If you are not shot dead.

Asking the stretcher bearers to go out there is asking them if they want to die.

Getting the rest of your platoon to start firing guarantees that the Germans will think something is going on and they'll respond with gunfire and mortar shells.