Answer:
A) The frequency of the dominant allele, C 
B) frequency of the heterozygous genotype, Cc 
Explanation:
Given -
Curly hair, C, is the dominant allele, and straight hair, c, is the recessive allele
Number of students with curly hair is 
Thus frequency of genotype "CC"

Thus, frequency of allele "q"

As per Hardy Weinberg's first equation-

Substituting the value of q, we get -

As per Hardy Weinberg's second equation -

Substituting the values of "p" and "q" we get -

Hence,
A) The frequency of the dominant allele, C 
B) frequency of the heterozygous genotype, Cc 