The correct response regarding a cause of the September 11 terror attacks by al-Qaeda is:
The U.S. maintained troops in Saudi Arabia after the invasion of Kuwait.
This presence was viewed by al-Qaeda and its leader, Osama bin Laden, as an occupation of Islamic holy land, which contributed to their grievances against the United States. The other options listed are related to different historical events and did not directly contribute to the motivations behind the September 11 attacks.