I must sit you must sit she must sit we must sit you must sit they must sit
V-ing form
I must be sitting you must be sitting she must be sitting we must be sitting you must be sitting they must be sitting
Perfect
I must have sat you must have sat she must have sat we must have sat you must have sat they must have sat
V-ing perfect
I must have been sitting you must have been sitting she must have been sitting we must have been sitting you must have been sitting they must have been sitting
Negation
Simple form
I must not sit you must not sit she must not sit we must not sit you must not sit they must not sit
V-ing form
I must not be sitting you must not be sitting she must not be sitting we must not be sitting you must not be sitting they must not be sitting
Perfect
I must not have sat you must not have sat she must not have sat we must not have sat you must not have sat they must not have sat
V-ing perfect
I must not have been sitting you must not have been sitting she must not have been sitting we must not have been sitting you must not have been sitting they must not have been sitting
Interrogative form
Simple form
must I sit? must you sit? must she sit? must we sit? must you sit? must they sit?
V-ing form
must I be sitting? must you be sitting? must she be sitting? must we be sitting? must you be sitting? must they be sitting?
Perfect
must I have sat? must you have sat? must she have sat? must we have sat? must you have sat? must they have sat?
V-ing perfect
must I have been sitting? must you have been sitting? must she have been sitting? must we have been sitting? must you have been sitting? must they have been sitting?
Interro-negative form
Simple form
must I not sit? must you not sit? must she not sit? must we not sit? must you not sit? must they not sit?
V-ing form
must I not be sitting? must you not be sitting? must she not be sitting? must we not be sitting? must you not be sitting? must they not be sitting?
Perfect
must I not have sat? must you not have sat? must she not have sat? must we not have sat? must you not have sat? must they not have sat?
V-ing perfect
must I not have been sitting? must you not have been sitting? must she not have been sitting? must we not have been sitting? must you not have been sitting? must they not have been sitting?