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