The hormone releasing IUDs function by:

Making the uterus unsuitable for implantation and the cervix hostile to the sperms

The correct answer is Option (4) - Making the uterus unsuitable for implantation and the cervix hostile to the sperms

The effective and popular method of contraception is the use of Intra Uterine Devices (IUDs). These devices are inserted by doctors or expert nurses in the uterus through vagina. These Intra Uterine Devices are presently available as the non-medicated IUDs (e.g., Lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and the hormone releasing IUDs (Progestasert, LNG-20). IUDs increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms. The hormonal-releasing IUD make the uterus unsuitable for implantation and the cervix hostile to the sperms.