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