I could undergo you could undergo she could undergo we could undergo you could undergo they could undergo
V-ing form
I could be undergoing you could be undergoing she could be undergoing we could be undergoing you could be undergoing they could be undergoing
Perfect
I could have undergone you could have undergone she 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 she 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 she 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 she 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 she 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 she 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 she undergo? could we undergo? could you undergo? could they undergo?
V-ing form
could I be undergoing? could you be undergoing? could she be undergoing? could we be undergoing? could you be undergoing? could they be undergoing?
Perfect
could I have undergone? could you have undergone? could she 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 she 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 she 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 she 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 she 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 she have been undergoing? couldn't we have been undergoing? couldn't you have been undergoing? couldn't they have been undergoing?