I could seal you could seal she could seal we could seal you could seal they could seal
V-ing form
I could be sealing you could be sealing she could be sealing we could be sealing you could be sealing they could be sealing
Perfect
I could have sealed you could have sealed she could have sealed we could have sealed you could have sealed they could have sealed
V-ing perfect
I could have been sealing you could have been sealing she could have been sealing we could have been sealing you could have been sealing they could have been sealing
Negation
Simple form
I couldn't seal you couldn't seal she couldn't seal we couldn't seal you couldn't seal they couldn't seal
V-ing form
I couldn't be sealing you couldn't be sealing she couldn't be sealing we couldn't be sealing you couldn't be sealing they couldn't be sealing
Perfect
I couldn't have sealed you couldn't have sealed she couldn't have sealed we couldn't have sealed you couldn't have sealed they couldn't have sealed
V-ing perfect
I couldn't have been sealing you couldn't have been sealing she couldn't have been sealing we couldn't have been sealing you couldn't have been sealing they couldn't have been sealing
Interrogative form
Simple form
could I seal? could you seal? could she seal? could we seal? could you seal? could they seal?
V-ing form
could I be sealing? could you be sealing? could she be sealing? could we be sealing? could you be sealing? could they be sealing?
Perfect
could I have sealed? could you have sealed? could she have sealed? could we have sealed? could you have sealed? could they have sealed?
V-ing perfect
could I have been sealing? could you have been sealing? could she have been sealing? could we have been sealing? could you have been sealing? could they have been sealing?
Interro-negative form
Simple form
couldn't I seal? couldn't you seal? couldn't she seal? couldn't we seal? couldn't you seal? couldn't they seal?
V-ing form
couldn't I be sealing? couldn't you be sealing? couldn't she be sealing? couldn't we be sealing? couldn't you be sealing? couldn't they be sealing?
Perfect
couldn't I have sealed? couldn't you have sealed? couldn't she have sealed? couldn't we have sealed? couldn't you have sealed? couldn't they have sealed?
V-ing perfect
couldn't I have been sealing? couldn't you have been sealing? couldn't she have been sealing? couldn't we have been sealing? couldn't you have been sealing? couldn't they have been sealing?