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