definitely "May"

The word it’s is always short for ‘it is’ (as in it's raining), or in informal speech, for ‘it has’ (as in it's got six legs). The word its means ‘belonging to it’ (as in hold its head still while I jump on its back). Its a possessive form and pronoun like his, her, their etc. so, it's=it is and its= possessive form of it.