Bill rides his bicycle 5.0 km [N], then 4.0 km [E], then 5.0 km [S], then 2.0 km [W]. in a total time of 2.0 h. What is his average speed for the trip?
A. 1.0 km/h
B. 4.0 km/h
C. 8.0 km/h
D. 16 km/h