There r four types of blood groups-
Since A has antibodies of B thus its donor grp are A& O
B has antibodies of A thus its donor grps are B& O
AB has no antibodies thus its donor grps are A, B, O. And thats y it is known as a universal acceptor
O has antibodies of A, B thus its donor grp is O itself since it only donates not accepts frm any other grp thus it is known as universal donor.
Hope u got ur ans