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