What type of submarine or u-boat sunk the rms Lusitania?

The German Submarine SM U-20 (1912), was a Type U 19 submarine launched in 1912 and that served in the First World War until grounded on 4 November 1916; notable for sinking RMS Lusitania

See:http://en.wikipedia.org/wiki/SM_U-20_(1912)

The sinking of the Cunard ocean liner RMS Lusitania occurred on 7 May 1915 during the First World War, as Germany waged submarine warfare against Britain. The ship was identified and shot by torpedoes by the German U-boat U- 20 and sank in 20 minutes. The vessel went down 11 miles (18 km) off the Old Head of Kinsale,Ireland, killing 1,198 and leaving 761 survivors. The sinking turned public opinion in many countries against Germany, contributed to the American entry into World War I and became an iconic symbol in military recruiting campaigns.

german I have no idea how many types they had

there were more like submersible boats than true submarines. Diesel powered battery operated

the L was not supposed to be carrying arms or ammunition

law of sea warfare was not well established.