I could retard you could retard she could retard we could retard you could retard they could retard
V-ing form
I could be retarding you could be retarding she could be retarding we could be retarding you could be retarding they could be retarding
Perfect
I could have retarded you could have retarded she could have retarded we could have retarded you could have retarded they could have retarded
V-ing perfect
I could have been retarding you could have been retarding she could have been retarding we could have been retarding you could have been retarding they could have been retarding
Negation
Simple form
I could not retard you could not retard she could not retard we could not retard you could not retard they could not retard
V-ing form
I could not be retarding you could not be retarding she could not be retarding we could not be retarding you could not be retarding they could not be retarding
Perfect
I could not have retarded you could not have retarded she could not have retarded we could not have retarded you could not have retarded they could not have retarded
V-ing perfect
I could not have been retarding you could not have been retarding she could not have been retarding we could not have been retarding you could not have been retarding they could not have been retarding
Interrogative form
Simple form
could I retard? could you retard? could she retard? could we retard? could you retard? could they retard?
V-ing form
could I be retarding? could you be retarding? could she be retarding? could we be retarding? could you be retarding? could they be retarding?
Perfect
could I have retarded? could you have retarded? could she have retarded? could we have retarded? could you have retarded? could they have retarded?
V-ing perfect
could I have been retarding? could you have been retarding? could she have been retarding? could we have been retarding? could you have been retarding? could they have been retarding?
Interro-negative form
Simple form
could I not retard? could you not retard? could she not retard? could we not retard? could you not retard? could they not retard?
V-ing form
could I not be retarding? could you not be retarding? could she not be retarding? could we not be retarding? could you not be retarding? could they not be retarding?
Perfect
could I not have retarded? could you not have retarded? could she not have retarded? could we not have retarded? could you not have retarded? could they not have retarded?
V-ing perfect
could I not have been retarding? could you not have been retarding? could she not have been retarding? could we not have been retarding? could you not have been retarding? could they not have been retarding?