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