Select the odd group of numbers. (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 /subtracting /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)

(7 - 70 - 68)

The logic followed here is :

Ist number × 10 = second number  and  second number - 10 =  third number

(6 - 60 - 50)

6 × 10 = 60 and  60 - 10 = 50

(8 - 80 - 70)

8 × 10 = 80 and  80 - 10 = 70

(9 - 90 -80)

9 × 10 = 90 and  90 - 10 = 80

Except option 2

(7 - 70 - 68)

9 × 10 = 90 and  90 - 10 = 80 which is odd