The correct answer is option 4 - article 377 of the Indian Penal Code (IPC) is related to unnatural sex. Article 377 deals with the prohibition of "unnatural offenses," which includes any sexual activity that is against the order of nature, such as homosexual intercourse. This section criminalized consensual same-sex relations and was widely criticized for being discriminatory and violating individual rights. However, in 2018, the Supreme Court of India decriminalized homosexuality by declaring section 377 unconstitutional. Therefore, it is important to note that as of now, consensual same-sex relations are no longer illegal under article 377 of the IPC.