I was doing a grammar exercise in the book Mastering Advanced English Language by Sara Thorne. Now, the exercise consisted of a paragraph of text where the reader has to label the pronouns in the text under various headings. When I checked the answers the pronouns "our", "their" and "my" were not listed as possessive pronouns - "ours", "mine" and "hers" were. Aren't these first set of pronouns (our, their, my) and the others like them (eg. your) still possessive pronouns, just in different forms, or not?