Fast its urgent
What do you mean by multi party system. With example​

A multi-party system is a system where multiple political parties take part in national elections. Each party has its own views. ... There is no limit to the number of parties that can take part in a British election, but the government must command a majority in the House of Commons, and is usually formed from one party.

well it depends i think people around the world are coming around to gay marriage. but if you are talking abortion then wow, so much to talk about. such as men thinking they have the right to choose if women can, the fact there are health concerns if the women can't get one, and many more arguments to discuss. so i would definitely say abortion would be a much more interesting topic.