Final answer:
The correct representation of normal human fertilization is C. n + n = 2n, where two haploid cells merge to form a diploid zygote.
Step-by-step explanation:
Normal Fertilization in Humans
Normal fertilization in humans involves the fusion of two haploid gametes (egg and sperm), each containing a single set of chromosomes (n), to form a diploid zygote (2n) with two sets of chromosomes. The correct representation of this process is C. n + n = 2n. This ensures that the offspring have the same chromosome number as their parents. Fertilization restores the diploid number by combining two haploid cells, a necessary part of the sexual reproduction cycle to maintain the species' chromosome count across generations.
Fertilization, pictured in Figure 43.23a, is crucial as it balances the halving of the chromosome number that occurs during meiosis, where gametes are produced. The cycle of sexual reproduction involves this alternation between diploid and haploid stages, with meiosis usually producing four haploid gametes, which fuse during fertilization to give rise to a diploid zygote.