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