Select the option that is related to the fifth number in the same way as the second number is related to the first number

Select the option that is related to the fifth number in the same way as the second number is related to the first number and the fourth number is related to the third number.

6 : 125 :: 2 : 1 :: 5 : ?

A.            81

B.            64

C.            68

D.            72

Sol:

Pattern follows here is:

If A : B then B : (A-1)³

Required number is: 5 : 64.