1.       You could be studying with Maria. 

2.       You must  turn off your cell phone while you are studying. 

3.       You must do your homework early. 

4.       you could do your homework later 

1.       you must not go late a class, remember  you missed yesterday. 

2.       you must be more organized with your time 

3.       you can't keep missing classes 

4.       You could leave your home earlier to avoid traffic. 

1.       You could be exercising with me. 

2.       She must train a lot, look how she is running. 

3.       She must participate in the competition, she is training very hard. 

4.       she must win, she is training