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