English verb conjugation
MUST OBSERVE

Regular verb: observe - observed - observed

Affirmation

Simple form	V-ing form
I must observe you must observe he must observe we must observe you must observe they must observe	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	V-ing 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	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

Negation

Simple form	V-ing form
I mustn't observe you mustn't observe he mustn't observe we mustn't observe you mustn't observe they mustn't observe	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	V-ing 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	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

Interrogative form

Simple form	V-ing form
must I observe? must you observe? must he observe? must we observe? must you observe? must they observe?	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	V-ing 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?	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?

Interro-negative form

Simple form	V-ing form
mustn't I observe? mustn't you observe? mustn't he observe? mustn't we observe? mustn't you observe? mustn't they observe?	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	V-ing 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?	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?