I must dust you must dust she must dust we must dust you must dust they must dust
V-ing form
I must be dusting you must be dusting she must be dusting we must be dusting you must be dusting they must be dusting
Perfect
I must have dusted you must have dusted she must have dusted we must have dusted you must have dusted they must have dusted
V-ing perfect
I must have been dusting you must have been dusting she must have been dusting we must have been dusting you must have been dusting they must have been dusting
Negation
Simple form
I must not dust you must not dust she must not dust we must not dust you must not dust they must not dust
V-ing form
I must not be dusting you must not be dusting she must not be dusting we must not be dusting you must not be dusting they must not be dusting
Perfect
I must not have dusted you must not have dusted she must not have dusted we must not have dusted you must not have dusted they must not have dusted
V-ing perfect
I must not have been dusting you must not have been dusting she must not have been dusting we must not have been dusting you must not have been dusting they must not have been dusting
Interrogative form
Simple form
must I dust? must you dust? must she dust? must we dust? must you dust? must they dust?
V-ing form
must I be dusting? must you be dusting? must she be dusting? must we be dusting? must you be dusting? must they be dusting?
Perfect
must I have dusted? must you have dusted? must she have dusted? must we have dusted? must you have dusted? must they have dusted?
V-ing perfect
must I have been dusting? must you have been dusting? must she have been dusting? must we have been dusting? must you have been dusting? must they have been dusting?
Interro-negative form
Simple form
must I not dust? must you not dust? must she not dust? must we not dust? must you not dust? must they not dust?
V-ing form
must I not be dusting? must you not be dusting? must she not be dusting? must we not be dusting? must you not be dusting? must they not be dusting?
Perfect
must I not have dusted? must you not have dusted? must she not have dusted? must we not have dusted? must you not have dusted? must they not have dusted?
V-ing perfect
must I not have been dusting? must you not have been dusting? must she not have been dusting? must we not have been dusting? must you not have been dusting? must they not have been dusting?