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