The correct answer is C - 315 metres ahead The shells are in the air for 21 seconds and the enemy ship moves at 15 metres per second. 21 seconds X 15 metres = 315 metres.

U-Boat Facts

Read the following facts concerning a Type VII U-Boat. Then answer the questions on the next screen:

Powered by 2 large diesel engines capable of 17 knots on the surface, a U-Boat spent 90% of its time on the surface. Once the order was given to dive, the diesel engines were shut down, and electric motors took over, using power being drawn from the boat's batteries. Undersea, the U-Boat was capable of a maximum speed of roughly 7 knots for only one hour. At a speed of only 2 knots, U-Boats had enough battery power to submerged for a maximum of 36 hours. It was then obliged to surface to replenish air and batteries. On the surface, a U-Boat using diesel power had the necessary speed to overtake a slow moving convoy, but underwater, under battery power, this was almost impossible. In most cases a "Condor" - a long distance German spotter plane - located the convoy. It then radioed the U-Boat command who contacted the U-Boat "wolfpack" and gave them the co-ordinates to set up an intercept. The convoy then blindly sailed right into the trap.

In the Spring of 1940, Jurgen Oesten was the commander of U-61. He noted that, 'All the boats we had during the war were basically surface craft that had the ability to dive. Out of the 20 ships I sank, 19 were sunk on the surface. At night, if you were closer to your target than 3000 to 4000 meters, then from the bridge of a normal merchantman, the U-Boat conning tower did not appear above the horizon. You offered only a small silhouette to your target, almost invisible.'

U-boats typically had up to six torpedo tubes: 4 aimed forwards, 2 aimed to the rear. A U-Boat could have up to thirty spare torpedoes stored inside. Most variations also had a single 4.1 or 5.9 inch deck cannon. Later versions were also armed with some form of anti-aircraft guns as a defense against Allied aircraft attacks.

Here is a short video on the basic features and operation of a U-Boat:

WW2 U-Boat in Colour, 2:29