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