I must cough you must cough she must cough we must cough you must cough they must cough
V-ing form
I must be coughing you must be coughing she must be coughing we must be coughing you must be coughing they must be coughing
Perfect
I must have coughed you must have coughed she must have coughed we must have coughed you must have coughed they must have coughed
V-ing perfect
I must have been coughing you must have been coughing she must have been coughing we must have been coughing you must have been coughing they must have been coughing
Negation
Simple form
I mustn't cough you mustn't cough she mustn't cough we mustn't cough you mustn't cough they mustn't cough
V-ing form
I mustn't be coughing you mustn't be coughing she mustn't be coughing we mustn't be coughing you mustn't be coughing they mustn't be coughing
Perfect
I mustn't have coughed you mustn't have coughed she mustn't have coughed we mustn't have coughed you mustn't have coughed they mustn't have coughed
V-ing perfect
I mustn't have been coughing you mustn't have been coughing she mustn't have been coughing we mustn't have been coughing you mustn't have been coughing they mustn't have been coughing
Interrogative form
Simple form
must I cough? must you cough? must she cough? must we cough? must you cough? must they cough?
V-ing form
must I be coughing? must you be coughing? must she be coughing? must we be coughing? must you be coughing? must they be coughing?
Perfect
must I have coughed? must you have coughed? must she have coughed? must we have coughed? must you have coughed? must they have coughed?
V-ing perfect
must I have been coughing? must you have been coughing? must she have been coughing? must we have been coughing? must you have been coughing? must they have been coughing?
Interro-negative form
Simple form
mustn't I cough? mustn't you cough? mustn't she cough? mustn't we cough? mustn't you cough? mustn't they cough?
V-ing form
mustn't I be coughing? mustn't you be coughing? mustn't she be coughing? mustn't we be coughing? mustn't you be coughing? mustn't they be coughing?
Perfect
mustn't I have coughed? mustn't you have coughed? mustn't she have coughed? mustn't we have coughed? mustn't you have coughed? mustn't they have coughed?
V-ing perfect
mustn't I have been coughing? mustn't you have been coughing? mustn't she have been coughing? mustn't we have been coughing? mustn't you have been coughing? mustn't they have been coughing?