During sexual differentiation in males:

Ans. is b, i.e. Primitive Gonads differentiate into testis due to the presence of SRY geneRef: Dutta Gynae 5th/ed, p420, 6th/ed, p439; Williams Gynae 1st/ed, p403-404; Harrison 17th/ed, p2339-2340In malesIn males --masculinization of external genitals begin at 9-10 weeks and is completed by 12-14 weeks of gestation.* Thereafter the only change is in the growth and length of penis.* Since in males, mainly masculinization is due to testosterone/dihydrotestosterone, therefore if it is deficient it will lead to under masculinization of external genitalia, i.e. males will have small phallus, hypospadias or scrotal defect, i.e. ambiguous genitalia.