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 could not attend you could not attend he could not attend we could not attend you could not attend they could not attend
V-ing form
I could not be attending you could not be attending he could not be attending we could not be attending you could not be attending they could not be attending
Perfect
I could not have attended you could not have attended he could not have attended we could not have attended you could not have attended they could not have attended
V-ing perfect
I could not have been attending you could not have been attending he could not have been attending we could not have been attending you could not have been attending they could not 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
could I not attend? could you not attend? could he not attend? could we not attend? could you not attend? could they not attend?
V-ing form
could I not be attending? could you not be attending? could he not be attending? could we not be attending? could you not be attending? could they not be attending?
Perfect
could I not have attended? could you not have attended? could he not have attended? could we not have attended? could you not have attended? could they not have attended?
V-ing perfect
could I not have been attending? could you not have been attending? could he not have been attending? could we not have been attending? could you not have been attending? could they not have been attending?