I could leaf you could leaf he could leaf we could leaf you could leaf they could leaf
V-ing form
I could be leafing you could be leafing he could be leafing we could be leafing you could be leafing they could be leafing
Perfect
I could have leafed you could have leafed he could have leafed we could have leafed you could have leafed they could have leafed
V-ing perfect
I could have been leafing you could have been leafing he could have been leafing we could have been leafing you could have been leafing they could have been leafing
Negation
Simple form
I could not leaf you could not leaf he could not leaf we could not leaf you could not leaf they could not leaf
V-ing form
I could not be leafing you could not be leafing he could not be leafing we could not be leafing you could not be leafing they could not be leafing
Perfect
I could not have leafed you could not have leafed he could not have leafed we could not have leafed you could not have leafed they could not have leafed
V-ing perfect
I could not have been leafing you could not have been leafing he could not have been leafing we could not have been leafing you could not have been leafing they could not have been leafing
Interrogative form
Simple form
could I leaf? could you leaf? could he leaf? could we leaf? could you leaf? could they leaf?
V-ing form
could I be leafing? could you be leafing? could he be leafing? could we be leafing? could you be leafing? could they be leafing?
Perfect
could I have leafed? could you have leafed? could he have leafed? could we have leafed? could you have leafed? could they have leafed?
V-ing perfect
could I have been leafing? could you have been leafing? could he have been leafing? could we have been leafing? could you have been leafing? could they have been leafing?
Interro-negative form
Simple form
could I not leaf? could you not leaf? could he not leaf? could we not leaf? could you not leaf? could they not leaf?
V-ing form
could I not be leafing? could you not be leafing? could he not be leafing? could we not be leafing? could you not be leafing? could they not be leafing?
Perfect
could I not have leafed? could you not have leafed? could he not have leafed? could we not have leafed? could you not have leafed? could they not have leafed?
V-ing perfect
could I not have been leafing? could you not have been leafing? could he not have been leafing? could we not have been leafing? could you not have been leafing? could they not have been leafing?