I could vibrate you could vibrate he could vibrate we could vibrate you could vibrate they could vibrate
V-ing form
I could be vibrating you could be vibrating he could be vibrating we could be vibrating you could be vibrating they could be vibrating
Perfect
I could have vibrated you could have vibrated he could have vibrated we could have vibrated you could have vibrated they could have vibrated
V-ing perfect
I could have been vibrating you could have been vibrating he could have been vibrating we could have been vibrating you could have been vibrating they could have been vibrating
Negation
Simple form
I couldn't vibrate you couldn't vibrate he couldn't vibrate we couldn't vibrate you couldn't vibrate they couldn't vibrate
V-ing form
I couldn't be vibrating you couldn't be vibrating he couldn't be vibrating we couldn't be vibrating you couldn't be vibrating they couldn't be vibrating
Perfect
I couldn't have vibrated you couldn't have vibrated he couldn't have vibrated we couldn't have vibrated you couldn't have vibrated they couldn't have vibrated
V-ing perfect
I couldn't have been vibrating you couldn't have been vibrating he couldn't have been vibrating we couldn't have been vibrating you couldn't have been vibrating they couldn't have been vibrating
Interrogative form
Simple form
could I vibrate? could you vibrate? could he vibrate? could we vibrate? could you vibrate? could they vibrate?
V-ing form
could I be vibrating? could you be vibrating? could he be vibrating? could we be vibrating? could you be vibrating? could they be vibrating?
Perfect
could I have vibrated? could you have vibrated? could he have vibrated? could we have vibrated? could you have vibrated? could they have vibrated?
V-ing perfect
could I have been vibrating? could you have been vibrating? could he have been vibrating? could we have been vibrating? could you have been vibrating? could they have been vibrating?
Interro-negative form
Simple form
couldn't I vibrate? couldn't you vibrate? couldn't he vibrate? couldn't we vibrate? couldn't you vibrate? couldn't they vibrate?
V-ing form
couldn't I be vibrating? couldn't you be vibrating? couldn't he be vibrating? couldn't we be vibrating? couldn't you be vibrating? couldn't they be vibrating?
Perfect
couldn't I have vibrated? couldn't you have vibrated? couldn't he have vibrated? couldn't we have vibrated? couldn't you have vibrated? couldn't they have vibrated?
V-ing perfect
couldn't I have been vibrating? couldn't you have been vibrating? couldn't he have been vibrating? couldn't we have been vibrating? couldn't you have been vibrating? couldn't they have been vibrating?