I must observe you must observe he must observe we must observe you must observe they must observe
Forme en V-ing
I must be observing you must be observing he must be observing we must be observing you must be observing they must be observing
Perfect
I must have observed you must have observed he must have observed we must have observed you must have observed they must have observed
Perfect en V-ing
I must have been observing you must have been observing he must have been observing we must have been observing you must have been observing they must have been observing
Négation
Forme simple
I mustn't observe you mustn't observe he mustn't observe we mustn't observe you mustn't observe they mustn't observe
Forme en V-ing
I mustn't be observing you mustn't be observing he mustn't be observing we mustn't be observing you mustn't be observing they mustn't be observing
Perfect
I mustn't have observed you mustn't have observed he mustn't have observed we mustn't have observed you mustn't have observed they mustn't have observed
Perfect en V-ing
I mustn't have been observing you mustn't have been observing he mustn't have been observing we mustn't have been observing you mustn't have been observing they mustn't have been observing
Forme interrogative
Forme simple
must I observe? must you observe? must he observe? must we observe? must you observe? must they observe?
Forme en V-ing
must I be observing? must you be observing? must he be observing? must we be observing? must you be observing? must they be observing?
Perfect
must I have observed? must you have observed? must he have observed? must we have observed? must you have observed? must they have observed?
Perfect en V-ing
must I have been observing? must you have been observing? must he have been observing? must we have been observing? must you have been observing? must they have been observing?
Forme interro-négative
Forme simple
mustn't I observe? mustn't you observe? mustn't he observe? mustn't we observe? mustn't you observe? mustn't they observe?
Forme en V-ing
mustn't I be observing? mustn't you be observing? mustn't he be observing? mustn't we be observing? mustn't you be observing? mustn't they be observing?
Perfect
mustn't I have observed? mustn't you have observed? mustn't he have observed? mustn't we have observed? mustn't you have observed? mustn't they have observed?
Perfect en V-ing
mustn't I have been observing? mustn't you have been observing? mustn't he have been observing? mustn't we have been observing? mustn't you have been observing? mustn't they have been observing?