Four pairs of numbers have been given, out of which three are alike in some manner, while one is different. Choose out the odd one.

73 - 79 31 - 41 61 - 71 83 - 97

73 - 79

1) 73 - 79, 73 and 79 are consecutive prime. 2) 31 - 41, There is 01 prime number between them. 3) 61 - 71,   There is 01 prime number between them. 4) 83 - 97, There is 01 prime number between them. Thus, 73 - 79 is the odd one.