Highway Engineering - Engineering

Q1:

On concrete roads, the camber generally provided, is

A 1 in 20 to 1 in 24

B 1 in 30 to 1 in 48

C 1 in 36 to 1 in 48

D 1 in 48 to 1 in 60

E 1 in 60 to 1 in 72

ANS:E - 1 in 60 to 1 in 72

How option D is correct? Please explain.