Q: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
During most of the war, the UN navies patrolled the west and east coasts of North Korea, sinking supply and ammunition ships and denying the North Koreans the ability to resupply from the sea. Aside from very occasional gunfire from North Korean shore batteries, the main threat to United States and UN navy ships was from magnetic mines. During the war, five U.S. Navy ships were lost to mines: two minesweepers, two minesweeper escorts, and one ocean tug. Mines and gunfire from North Korean coastal artillery damaged another 87 U.S. warships, resulting in slight to moderate damage.
A:
What type of ships did the US spend most of its time sinking?