In Hardy-Weinberg contexts under selection, how are allele frequencies updated after fitness differences among genotypes?

• A. Allele frequencies are unaffected by selection and stay at p and q.
• B. Allele frequencies are reversed so p becomes q and q becomes p.
• C. p and q are adjusted by the relative fitness of each genotype and renormalized.
• D. Only homozygous frequencies change; heterozygote remains constant.

Answer: (C)