I could deepen you could deepen she could deepen we could deepen you could deepen they could deepen
V-ing form
I could be deepening you could be deepening she could be deepening we could be deepening you could be deepening they could be deepening
Perfect
I could have deepened you could have deepened she 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 she 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 she 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 she 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 she 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 she 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 she deepen? could we deepen? could you deepen? could they deepen?
V-ing form
could I be deepening? could you be deepening? could she be deepening? could we be deepening? could you be deepening? could they be deepening?
Perfect
could I have deepened? could you have deepened? could she 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 she 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 she 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 she 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 she 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 she have been deepening? couldn't we have been deepening? couldn't you have been deepening? couldn't they have been deepening?