English verb conjugation
COULD OBSERVE

Regular verb: observe - observed - observed

Affirmation

Simple form	V-ing form
I could observe you could observe she could observe we could observe you could observe they could observe	I could be observing you could be observing she could be observing we could be observing you could be observing they could be observing
Perfect	V-ing perfect
I could have observed you could have observed she could have observed we could have observed you could have observed they could have observed	I could have been observing you could have been observing she could have been observing we could have been observing you could have been observing they could have been observing

Negation

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

Interrogative form

Simple form	V-ing form
could I observe? could you observe? could she observe? could we observe? could you observe? could they observe?	could I be observing? could you be observing? could she be observing? could we be observing? could you be observing? could they be observing?
Perfect	V-ing perfect
could I have observed? could you have observed? could she have observed? could we have observed? could you have observed? could they have observed?	could I have been observing? could you have been observing? could she have been observing? could we have been observing? could you have been observing? could they have been observing?

Interro-negative form

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