Gametes have half the chromosome number of somatic cells

Steps:

• Muscle cells are somatic and diploid (2n), so 2n = 64 chromosomes.
• Diploid cells contain paired chromosomes from both parents.
• Sperm cells are gametes produced by meiosis, making them haploid (n).
• Haploid number n = 64 / 2 = 32 chromosomes.

Why B is correct:

• In meiosis, diploid cells divide to form haploid gametes with half the chromosome number (n = 2n / 2), so sperm has 32 chromosomes.

Why the others are wrong:

• A: 23 is the human haploid number, not applicable to horses.
• C: 64 matches the diploid somatic cell count, not haploid gametes.
• D: 128 would imply a doubling (tetraploid), which does not occur in normal gamete formation.

Final answer: B