What was the cause of the sinking of the "Lusitania" in May 1915 and the subsequent deaths of 1,198 people?

Question

The HMHS Britannic, sister ship to the Titanic and heir to the experience gained by that sinking, was completed at the end of 1915 and requisitioned as what before falling foul of a mine and sinking in 1916?

Answer 1

She was torpedoed
She was torpedoed by German U-boat U-20 and sank in eighteen minutes, eleven miles (19 km) off the Old Head of Kinsale, Ireland, killing about 1,198 of the 1,959 people aboard. The sinking turned public opinion in many countries against Germany and contributed to the entry of the United States into World War I.