Right choice is (a) 10
Easy explanation: The squares of the numbers 5 & 6 are 25 & 36 respectively. There are 10 numbers between 25 and 36 (i.e. 26, 27, 28, 29, 30, 31, 32, 33, 34, 35). Therefore, the correct answer would be 10 and the others would be incorrect.