I can sell you can sell he can sell we can sell you can sell they can sell
V-ing form
I can be selling you can be selling he can be selling we can be selling you can be selling they can be selling
Perfect
I can have sold you can have sold he can have sold we can have sold you can have sold they can have sold
V-ing perfect
I can have been selling you can have been selling he can have been selling we can have been selling you can have been selling they can have been selling
Negation
Simple form
I can't sell you can't sell he can't sell we can't sell you can't sell they can't sell
V-ing form
I can't be selling you can't be selling he can't be selling we can't be selling you can't be selling they can't be selling
Perfect
I can't have sold you can't have sold he can't have sold we can't have sold you can't have sold they can't have sold
V-ing perfect
I can't have been selling you can't have been selling he can't have been selling we can't have been selling you can't have been selling they can't have been selling
Interrogative form
Simple form
can I sell? can you sell? can he sell? can we sell? can you sell? can they sell?
V-ing form
can I be selling? can you be selling? can he be selling? can we be selling? can you be selling? can they be selling?
Perfect
can I have sold? can you have sold? can he have sold? can we have sold? can you have sold? can they have sold?
V-ing perfect
can I have been selling? can you have been selling? can he have been selling? can we have been selling? can you have been selling? can they have been selling?
Interro-negative form
Simple form
can't I sell? can't you sell? can't he sell? can't we sell? can't you sell? can't they sell?
V-ing form
can't I be selling? can't you be selling? can't he be selling? can't we be selling? can't you be selling? can't they be selling?
Perfect
can't I have sold? can't you have sold? can't he have sold? can't we have sold? can't you have sold? can't they have sold?
V-ing perfect
can't I have been selling? can't you have been selling? can't he have been selling? can't we have been selling? can't you have been selling? can't they have been selling?