In a random mating population frequency of recessive allele is $0.5$. What is the frequency of dominant phenotypes in population?

The correct option is C $0.75$
In the given problem, frequency of recessive allele (q) is 0.5.

Hence, the frequency of dominant allele (p) is 1 - q = 1 - 0.5 = 0.5.

Frequency of homozygous dominant = p${}^2$ = 0.25.

Frequency of heterozygous dominant = 2pq = 2 * 0.5 * 0.5 = 0.5.

Hence, frequency of dominant phenotypes in a population = Frequency of homozygous dominant + Frequency of heterozygous dominant = 0.5 + 0.25 = 0.75.

Thus, the correct answer is '0.75'.