Assume that the moon takes exactly 30 days to complete the cycle and also assume that it rises in the East exactly at 6.48 p.m. on the first day. On the fourth day, at what time will it rise?

To find the moonrise time on the fourth day, we first calculate the daily delay in the moonrise.

A full circle of 360 degrees is covered in 24 hours. Since the moon takes 30 days to complete its cycle, it shifts by 12 degrees each day (360 divided by 30).

Because the Earth rotates 360 degrees in 24 hours, it rotates at a rate of 1 degree every 4 minutes. Therefore, a shift of 12 degrees results in a daily delay of 48 minutes (12 multiplied by 4).

On the first day, the moon rises at 6.48 p.m. On the second day, it rises 48 minutes later. On the third day, it rises 96 minutes later. On the fourth day, it rises 144 minutes later (48 minutes multiplied by 3 intervals).

144 minutes is equal to 2 hours and 24 minutes. Adding 2 hours and 24 minutes to 6.48 p.m. gives 9.12 p.m.

Thus, option B is correct.