A student on his birthday distributed an average 5 chocolates per student. If on the arrival of the teacher and the headmaster to when the student gives 10 and 15 chocolates respectively, the average chocolate distributed per head increases to 5.5, then what is the number of students in the class?(a) 28(b) 30(c) 32(d) 36

Let the total number of students in the class be \( n \).

Initially, the student distributes an average of 5 chocolates per student. Thus, the total chocolates distributed to the students is:
\[ 5n \]

When the teacher and headmaster arrive, the student gives them 10 and 15 chocolates respectively. The total number of people now becomes \( n + 2 \) (including the teacher and headmaster).

The total chocolates distributed becomes:
\[ 5n + 10 + 15 = 5n + 25 \]

The new average number of chocolates distributed per person is 5.5. Therefore, we have the equation:
\[
\text{New Average} = \frac{\text{Total Chocolates}}{\text{Total People}}
\]
\[
5.5 = \frac{5n + 25}{n + 2}
\]

Multiply through by \( n + 2 \) to eliminate the fraction:
\[
5.5(n + 2) = 5n + 25
\]
\[
5.5n + 11 = 5n + 25
\]

Simplify the equation:
\[
5.5n - 5n = 25 - 11
\]
\[
0.5n = 14
\]

Solve for \( n \):
\[
n = \frac{14}{0.5} = 28
\]

Thus, the number of students in the class is:
**28**

Answer: (a) 28