Alright Olaide — let's do this. The question asks which of the listed options is not part of the mammalian male reproductive organ. A) The epididymis* is a coiled tube located at the back of each testis, where sperm mature and are stored. It is part of the male reproductive system. B) The vas deferens* (also called sperm duct) is a tube that transports sperm from the epididymis to the ejaculatory ducts. It is part of the male reproductive system. C) The testis* (plural: testes) is the primary male reproductive organ, responsible for producing sperm and male hormones like testosterone. It is part of the male reproductive system. D) The vulva* refers to the external female genitalia. It is not part of the male reproductive system. Therefore, the vulva is not a part of the mammalian male reproductive organ. The final answer is $\boxed{\text{D}}$ Got more? Send 'em!