Select the option in which the numbers are related in the same way as are the numbers in the following sets. 

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding /deleting /multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed)

(16, 18, 20)
(17, 19, 21)

(64, 66, 68)

(16, 18, 20)
(17, 19, 21)

The logic followed here is :

Ist number + 2 =  second number and  second number + 2 = IIIrd number

as

16 +2 = 18 and 18 +2 = 20

17 +2 = 19 and  19 + 2 = 21

Therefore

In this option (64, 66, 68)

64 +2 = 66 and 66 +2 = 68