I must serve you must serve he must serve we must serve you must serve they must serve
V-ing form
I must be serving you must be serving he must be serving we must be serving you must be serving they must be serving
Perfect
I must have served you must have served he must have served we must have served you must have served they must have served
V-ing perfect
I must have been serving you must have been serving he must have been serving we must have been serving you must have been serving they must have been serving
Negation
Simple form
I must not serve you must not serve he must not serve we must not serve you must not serve they must not serve
V-ing form
I must not be serving you must not be serving he must not be serving we must not be serving you must not be serving they must not be serving
Perfect
I must not have served you must not have served he must not have served we must not have served you must not have served they must not have served
V-ing perfect
I must not have been serving you must not have been serving he must not have been serving we must not have been serving you must not have been serving they must not have been serving
Interrogative form
Simple form
must I serve? must you serve? must he serve? must we serve? must you serve? must they serve?
V-ing form
must I be serving? must you be serving? must he be serving? must we be serving? must you be serving? must they be serving?
Perfect
must I have served? must you have served? must he have served? must we have served? must you have served? must they have served?
V-ing perfect
must I have been serving? must you have been serving? must he have been serving? must we have been serving? must you have been serving? must they have been serving?
Interro-negative form
Simple form
must I not serve? must you not serve? must he not serve? must we not serve? must you not serve? must they not serve?
V-ing form
must I not be serving? must you not be serving? must he not be serving? must we not be serving? must you not be serving? must they not be serving?
Perfect
must I not have served? must you not have served? must he not have served? must we not have served? must you not have served? must they not have served?
V-ing perfect
must I not have been serving? must you not have been serving? must he not have been serving? must we not have been serving? must you not have been serving? must they not have been serving?