6.33 The average age of the students is 11 years old, and the average age of the 55 parents of these students is 33 years old. Then the overall average age of all students and parents is ( ) years old.
(A) 22
(B) 23.25
(C) 24.75
(D) 26.25
(E) 28
6. C.
$$
\bar{x}=\frac{33 \times 11+55 \times 33}{33+55}=24.75 .
$$