English verb conjugation
MUST OBSERVE

Regular verb: observe - observed - observed

Affirmation

Simple form	V-ing form
I must observe you must observe she must observe we must observe you must observe they must observe	I must be observing you must be observing she 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 she 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 she 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 must not observe you must not observe she must not observe we must not observe you must not observe they must not observe	I must not be observing you must not be observing she must not be observing we must not be observing you must not be observing they must not be observing
Perfect	V-ing perfect
I must not have observed you must not have observed she must not have observed we must not have observed you must not have observed they must not have observed	I must not have been observing you must not have been observing she must not have been observing we must not have been observing you must not have been observing they must not have been observing

Interrogative form

Simple form	V-ing form
must I observe? must you observe? must she observe? must we observe? must you observe? must they observe?	must I be observing? must you be observing? must she 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 she 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 she 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
must I not observe? must you not observe? must she not observe? must we not observe? must you not observe? must they not observe?	must I not be observing? must you not be observing? must she not be observing? must we not be observing? must you not be observing? must they not be observing?
Perfect	V-ing perfect
must I not have observed? must you not have observed? must she not have observed? must we not have observed? must you not have observed? must they not have observed?	must I not have been observing? must you not have been observing? must she not have been observing? must we not have been observing? must you not have been observing? must they not have been observing?