• Approach to Hardy-Weinberg Equilibrium for Sex-Linked (X-Linked) Genes:
• Because heterogametic males ($XY$) receive their single X chromosome exclusively from their mother, whereas homogametic females ($XX$) receive one X from each parent:
• In each successive generation of random mating, the difference in allele frequency between males ($q_m$) and females ($q_f$) is:

• Thus, the difference between the frequencies in the two sexes is half the difference in the previous generation, but in the opposite direction, oscillating in a damped harmonic series until converging to equilibrium:

• nalysis:
• Correct mathematical description of sex-linked allele frequency dynamics.

Correct option: (4) is half the differences in the previous generation, but in other direction