Hi,
Seeing the stats alone will definitely not yield an aswer since we have not restriction on the number of students we have.

However combining the 2 stats we can have only 2 values of the total number of students ,
1>either 20 so that 10% of 20 gives and integer = 2 {this is barred by stat 1}
2>or 10 so that 10% of 10 gives an integer = 1

All other values of integers between 1 and 20 will give non integer values when u take 10% of the same.

hence the correct answer is C

C

obviously both the options do not independently converge to some answer.

Taking both (1) and (2),

since the number of students, or for that matter, number of boys, has to be an integer.

And the only integer values that satisfy the conditions are,

Total no. of students = 10
and thus, no. of boys = 10% of 10 = 1

So, answer should be C