I must look you must look he must look we must look you must look they must look
V-ing form
I must be looking you must be looking he must be looking we must be looking you must be looking they must be looking
Perfect
I must have looked you must have looked he must have looked we must have looked you must have looked they must have looked
V-ing perfect
I must have been looking you must have been looking he must have been looking we must have been looking you must have been looking they must have been looking
Negation
Simple form
I mustn't look you mustn't look he mustn't look we mustn't look you mustn't look they mustn't look
V-ing form
I mustn't be looking you mustn't be looking he mustn't be looking we mustn't be looking you mustn't be looking they mustn't be looking
Perfect
I mustn't have looked you mustn't have looked he mustn't have looked we mustn't have looked you mustn't have looked they mustn't have looked
V-ing perfect
I mustn't have been looking you mustn't have been looking he mustn't have been looking we mustn't have been looking you mustn't have been looking they mustn't have been looking
Interrogative form
Simple form
must I look? must you look? must he look? must we look? must you look? must they look?
V-ing form
must I be looking? must you be looking? must he be looking? must we be looking? must you be looking? must they be looking?
Perfect
must I have looked? must you have looked? must he have looked? must we have looked? must you have looked? must they have looked?
V-ing perfect
must I have been looking? must you have been looking? must he have been looking? must we have been looking? must you have been looking? must they have been looking?
Interro-negative form
Simple form
mustn't I look? mustn't you look? mustn't he look? mustn't we look? mustn't you look? mustn't they look?
V-ing form
mustn't I be looking? mustn't you be looking? mustn't he be looking? mustn't we be looking? mustn't you be looking? mustn't they be looking?
Perfect
mustn't I have looked? mustn't you have looked? mustn't he have looked? mustn't we have looked? mustn't you have looked? mustn't they have looked?
V-ing perfect
mustn't I have been looking? mustn't you have been looking? mustn't he have been looking? mustn't we have been looking? mustn't you have been looking? mustn't they have been looking?