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