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