<prompt> During sexual differentiation in males:Leydig cells produce Mullerian Inhibiting SubstancePrimitive Gonads differentiate into testis due to the presence of SRY geneAndrogen binding protein is responsible for the development of male external GenitaliaWolffian duct regresses  <response>: Ans. is b, i.e. Primitive Gonads differentiate into testis due to the presence of SRY geneRef: Dutta Gynae 5thed, p420, 6thed, p439; Williams Gynae 1sted, p403-404; Harrison 17thed, 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 testosteronedihydrotestosterone, 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. 