At the time of implantation, the human embryo is called a/an:

Arrange the following cell layers/structures around the female gamete, from outer to inner side: A. Zona pellucida B. Perivitelline space C. Corona radiata D. Plasma membrane of ovum Choose the correct answer from the options given below:

Spermatogonia undergo a series of cell divisions to produce sperms. Consider the following statements: A. Spermatogonia always undergo meiotic cell division. B. Primary spermatocytes divide mitotically to produce secondary spermatocytes. C. Secondary spermatocytes, through their second meiotic division, produce haploid spermatids. D. Spermatids produce spermatozoa through mitosis. E. Spermatids transform into spermatozoa by spermiogenesis. Choose the correct answer from the options given below: