Question: In one day, a family in a car rode for 2 hours, stopped for 3 hours, and then rode for another 5 hours. During the day, the family traveled a total distance of 400 kilometers. What was their average speed for the whole trip?

  Options: 
 A. 10 km/h
 B. 20 km/h
 C. 40 km/h
 D. 50 km/h
Answer: C