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)

5 - 31

The logic followed here is :

(Ist number)² - 10  = second number

13 - 159 = 13² - 10 =159

9 - 71 = 9² - 10 = 71

5 - 31 = 5² - 10 = 15 but 31 is given Odd

17 - 279 = 17 ² - 10 = 279