I could congregate you could congregate she could congregate we could congregate you could congregate they could congregate
V-ing form
I could be congregating you could be congregating she could be congregating we could be congregating you could be congregating they could be congregating
Perfect
I could have congregated you could have congregated she could have congregated we could have congregated you could have congregated they could have congregated
V-ing perfect
I could have been congregating you could have been congregating she could have been congregating we could have been congregating you could have been congregating they could have been congregating
Negation
Simple form
I could not congregate you could not congregate she could not congregate we could not congregate you could not congregate they could not congregate
V-ing form
I could not be congregating you could not be congregating she could not be congregating we could not be congregating you could not be congregating they could not be congregating
Perfect
I could not have congregated you could not have congregated she could not have congregated we could not have congregated you could not have congregated they could not have congregated
V-ing perfect
I could not have been congregating you could not have been congregating she could not have been congregating we could not have been congregating you could not have been congregating they could not have been congregating
Interrogative form
Simple form
could I congregate? could you congregate? could she congregate? could we congregate? could you congregate? could they congregate?
V-ing form
could I be congregating? could you be congregating? could she be congregating? could we be congregating? could you be congregating? could they be congregating?
Perfect
could I have congregated? could you have congregated? could she have congregated? could we have congregated? could you have congregated? could they have congregated?
V-ing perfect
could I have been congregating? could you have been congregating? could she have been congregating? could we have been congregating? could you have been congregating? could they have been congregating?
Interro-negative form
Simple form
could I not congregate? could you not congregate? could she not congregate? could we not congregate? could you not congregate? could they not congregate?
V-ing form
could I not be congregating? could you not be congregating? could she not be congregating? could we not be congregating? could you not be congregating? could they not be congregating?
Perfect
could I not have congregated? could you not have congregated? could she not have congregated? could we not have congregated? could you not have congregated? could they not have congregated?
V-ing perfect
could I not have been congregating? could you not have been congregating? could she not have been congregating? could we not have been congregating? could you not have been congregating? could they not have been congregating?