I must buy you must buy he must buy we must buy you must buy they must buy
V-ing form
I must be buying you must be buying he must be buying we must be buying you must be buying they must be buying
Perfect
I must have bought you must have bought he must have bought we must have bought you must have bought they must have bought
V-ing perfect
I must have been buying you must have been buying he must have been buying we must have been buying you must have been buying they must have been buying
Negation
Simple form
I must not buy you must not buy he must not buy we must not buy you must not buy they must not buy
V-ing form
I must not be buying you must not be buying he must not be buying we must not be buying you must not be buying they must not be buying
Perfect
I must not have bought you must not have bought he must not have bought we must not have bought you must not have bought they must not have bought
V-ing perfect
I must not have been buying you must not have been buying he must not have been buying we must not have been buying you must not have been buying they must not have been buying
Interrogative form
Simple form
must I buy? must you buy? must he buy? must we buy? must you buy? must they buy?
V-ing form
must I be buying? must you be buying? must he be buying? must we be buying? must you be buying? must they be buying?
Perfect
must I have bought? must you have bought? must he have bought? must we have bought? must you have bought? must they have bought?
V-ing perfect
must I have been buying? must you have been buying? must he have been buying? must we have been buying? must you have been buying? must they have been buying?
Interro-negative form
Simple form
must I not buy? must you not buy? must he not buy? must we not buy? must you not buy? must they not buy?
V-ing form
must I not be buying? must you not be buying? must he not be buying? must we not be buying? must you not be buying? must they not be buying?
Perfect
must I not have bought? must you not have bought? must he not have bought? must we not have bought? must you not have bought? must they not have bought?
V-ing perfect
must I not have been buying? must you not have been buying? must he not have been buying? must we not have been buying? must you not have been buying? must they not have been buying?