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