I must cough you must cough he must cough we must cough you must cough they must cough
V-ing form
I must be coughing you must be coughing he must be coughing we must be coughing you must be coughing they must be coughing
Perfect
I must have coughed you must have coughed he 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 he 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 he 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 he 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 he 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 he 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 he cough? must we cough? must you cough? must they cough?
V-ing form
must I be coughing? must you be coughing? must he be coughing? must we be coughing? must you be coughing? must they be coughing?
Perfect
must I have coughed? must you have coughed? must he 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 he 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 he 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 he 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 he 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 he have been coughing? mustn't we have been coughing? mustn't you have been coughing? mustn't they have been coughing?