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