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

12 : 36 :: 18 : 81 :: 56 : ?

784

Pattern followed here is :

12 : 36

6×2 : square of 6

12 : 36

& 18 : 81

9×2 : square of 9

18 : 81

Similarly ,

56 : ?

28×2 : square of 28

56 : 784

56 : 784  , is correct answer .