Answer : 1. "86"
Explanation :

Answer: A) 86 Explanation: Here the given number series is 5  11  21  44  ?  175   Now the given series follows a pattern, that   x2 + 1, x2 - 1, x2 + 2, x2 - 2, x2 + 3, x2 - 3,...   Then the missing number is x2 - 2   = 44 x 2 - 2 = 88 - 2 = 86   Hence, the missing number in the number series is 86.