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