Answer :
C. 5.
1 hour/5 miles
1 hour/5 miles 5x2=10
1 hour/5 miles
1 hour/5 miles 5x4=20
1 hour/5 miles
5x5=25
1 hour/5 miles
1 hour/5 miles 5x2=10
1 hour/5 miles
1 hour/5 miles 5x4=20
1 hour/5 miles
5x5=25