1) I ..... be really mean to her, but i don't want to treat her like that 2) You .... Follow the law or yoy will go to jail 3)I .... Go to the wedding. I have to work on the same day

1 I could be really mean  2 you must follow  3 I can't go 

1) I can be really mean to her, but i don't want to treat her like that. 2) You must follow the law or you will go to jail. 3)I can't go to the wedding. I have to work on the same day.