I would say "A," going to sleep. I hesitate to recommend B because at least in the United States, we do not generally say "falling to sleep." We definitely do say "falling asleep." There may be a minority of speakers who say "fall to sleep," as evidenced by the following hits doing a Google search: Google (UK pages) gives: "fall to sleep" : 837 "fall asleep" : 102,000 "go to sleep" : 103,000

Hi, both words can fit into the gap :) Your right, if you use 'falling',then it will be 'falling asleep'. So: The noise of the traffic prevented me from going to sleep. The noise of the traffic prevented me from falling sleep.