I could blister you could blister she could blister we could blister you could blister they could blister
V-ing form
I could be blistering you could be blistering she could be blistering we could be blistering you could be blistering they could be blistering
Perfect
I could have blistered you could have blistered she could have blistered we could have blistered you could have blistered they could have blistered
V-ing perfect
I could have been blistering you could have been blistering she could have been blistering we could have been blistering you could have been blistering they could have been blistering
Negation
Simple form
I couldn't blister you couldn't blister she couldn't blister we couldn't blister you couldn't blister they couldn't blister
V-ing form
I couldn't be blistering you couldn't be blistering she couldn't be blistering we couldn't be blistering you couldn't be blistering they couldn't be blistering
Perfect
I couldn't have blistered you couldn't have blistered she couldn't have blistered we couldn't have blistered you couldn't have blistered they couldn't have blistered
V-ing perfect
I couldn't have been blistering you couldn't have been blistering she couldn't have been blistering we couldn't have been blistering you couldn't have been blistering they couldn't have been blistering
Interrogative form
Simple form
could I blister? could you blister? could she blister? could we blister? could you blister? could they blister?
V-ing form
could I be blistering? could you be blistering? could she be blistering? could we be blistering? could you be blistering? could they be blistering?
Perfect
could I have blistered? could you have blistered? could she have blistered? could we have blistered? could you have blistered? could they have blistered?
V-ing perfect
could I have been blistering? could you have been blistering? could she have been blistering? could we have been blistering? could you have been blistering? could they have been blistering?
Interro-negative form
Simple form
couldn't I blister? couldn't you blister? couldn't she blister? couldn't we blister? couldn't you blister? couldn't they blister?
V-ing form
couldn't I be blistering? couldn't you be blistering? couldn't she be blistering? couldn't we be blistering? couldn't you be blistering? couldn't they be blistering?
Perfect
couldn't I have blistered? couldn't you have blistered? couldn't she have blistered? couldn't we have blistered? couldn't you have blistered? couldn't they have blistered?
V-ing perfect
couldn't I have been blistering? couldn't you have been blistering? couldn't she have been blistering? couldn't we have been blistering? couldn't you have been blistering? couldn't they have been blistering?