Nokea
The phenotypic sex is determined by:
Correct Answer: D
Rationale: Step-by-step rationale for why choice D is correct:
1. During early development, all embryos possess indifferent genitalia.
2. Androgen hormones, like testosterone, influence the differentiation of these structures.
3. The presence of androgen hormones leads to the development of male genitalia.
4. Lack of androgen results in the development of female genitalia.
5. This process occurs after fertilization, not during fertilization.
In summary, choice D is correct as the phenotypic sex is determined by the activity of androgen hormones on the indifferent genitalia post-fertilization.
Choices A and B are incorrect because sex determination occurs post-fertilization, not during fertilization.
Choice C is incorrect as the SRY gene typically plays a role in sex determination but is not the primary factor influencing the phenotypic sex.