You can use either. You may find this page useful: http://learnenglish.britishcouncil.org/en/english-grammar/pronouns/that-these-and-those "Those" is often used with things that are not close by. "They" could be used for nearby or distant things. So, think about where the pants are when deciding which is the best to use.

Wow there are so many answers, because of different versions of English. However, and in the absence of context, since the question refers to 'those', I would go for A2.

They're both correct.