I can sell you can sell she can sell we can sell you can sell they can sell
V-ing form
I can be selling you can be selling she can be selling we can be selling you can be selling they can be selling
Perfect
I can have sold you can have sold she 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 she 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 she 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 she 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 she 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 she 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 she sell? can we sell? can you sell? can they sell?
V-ing form
can I be selling? can you be selling? can she be selling? can we be selling? can you be selling? can they be selling?
Perfect
can I have sold? can you have sold? can she 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 she 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 she 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 she 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 she 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 she have been selling? can't we have been selling? can't you have been selling? can't they have been selling?