The event which started the Gulf War in 1991 was a) the invasion of Kuwait by Iraq. There were the largest amount of coalition forces during this war since World War II, with most of them being from the United States, the United Kingdom, Saudi Arabia and Egypt fighting for Iraq to immediately stop it's invasion and annexation of Kuwait.
The answer is A. Imagine the 3 in 13 as a handcuff and the 1 as the key unlocking it