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