How many odd integers from 1 to 100 (both inclusive) have odd number of factors?  Choose the correct option.
A) 13 B) 14 C) 5 D) 6 E) 7

Rationale: integers having odd number of factors will be perfect squares . odd numbers will have odd perfect squares . thus , the possible values for the perfect squares are : 1 , 9,25 , 49,81 and the corresponding integers are 1 , 3,5 , 7,9 ( more than 4 ) . thus c is the correct answer .
Answer: C