Final answer:
Edmund Hillary and Tenzing Norgay began their successful ascent to the summit of Mount Everest at 6:30 a.m. on May 29, 1953.
Step-by-step explanation:
The question asks about the time of day when Sir Edmund Hillary and Tenzing Norgay began their final ascent to the summit of Mount Everest. The correct answer is c) 6:30 a.m. On May 29, 1953, Hillary and Norgay set out for the summit in the early morning hours and reached the top of the world at around 11:30 a.m. Their ascent was a significant historical event as they were the first confirmed climbers to successfully reach the summit of Mount Everest.