English verb conjugation
CAN OBSERVE

Regular verb: observe - observed - observed

Affirmation

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

Negation

Simple form	V-ing form
I can't observe you can't observe he can't observe we can't observe you can't observe they can't observe	I can't be observing you can't be observing he can't be observing we can't be observing you can't be observing they can't be observing
Perfect	V-ing perfect
I can't have observed you can't have observed he can't have observed we can't have observed you can't have observed they can't have observed	I can't have been observing you can't have been observing he can't have been observing we can't have been observing you can't have been observing they can't have been observing

Interrogative form

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

Interro-negative form

Simple form	V-ing form
can't I observe? can't you observe? can't he observe? can't we observe? can't you observe? can't they observe?	can't I be observing? can't you be observing? can't he be observing? can't we be observing? can't you be observing? can't they be observing?
Perfect	V-ing perfect
can't I have observed? can't you have observed? can't he have observed? can't we have observed? can't you have observed? can't they have observed?	can't I have been observing? can't you have been observing? can't he have been observing? can't we have been observing? can't you have been observing? can't they have been observing?