The number of miles Earth travels in its one-year orbit of the Sun is 580,000,000. Because there are about 365 days per year, the number of miles Earth travels per day is
≈1,589,041. There are 24 hours in one day, so Earth travels at
≈66,210 miles per hour. Therefore, of the choices given, 66,000 miles per hour is closest to the average speed of Earth as it orbits the Sun.
Choices B, C, and D are incorrect and may result from calculation errors.