I could weaken you could weaken she could weaken we could weaken you could weaken they could weaken
V-ing form
I could be weakening you could be weakening she could be weakening we could be weakening you could be weakening they could be weakening
Perfect
I could have weakened you could have weakened she could have weakened we could have weakened you could have weakened they could have weakened
V-ing perfect
I could have been weakening you could have been weakening she could have been weakening we could have been weakening you could have been weakening they could have been weakening
Negation
Simple form
I could not weaken you could not weaken she could not weaken we could not weaken you could not weaken they could not weaken
V-ing form
I could not be weakening you could not be weakening she could not be weakening we could not be weakening you could not be weakening they could not be weakening
Perfect
I could not have weakened you could not have weakened she could not have weakened we could not have weakened you could not have weakened they could not have weakened
V-ing perfect
I could not have been weakening you could not have been weakening she could not have been weakening we could not have been weakening you could not have been weakening they could not have been weakening
Interrogative form
Simple form
could I weaken? could you weaken? could she weaken? could we weaken? could you weaken? could they weaken?
V-ing form
could I be weakening? could you be weakening? could she be weakening? could we be weakening? could you be weakening? could they be weakening?
Perfect
could I have weakened? could you have weakened? could she have weakened? could we have weakened? could you have weakened? could they have weakened?
V-ing perfect
could I have been weakening? could you have been weakening? could she have been weakening? could we have been weakening? could you have been weakening? could they have been weakening?
Interro-negative form
Simple form
could I not weaken? could you not weaken? could she not weaken? could we not weaken? could you not weaken? could they not weaken?
V-ing form
could I not be weakening? could you not be weakening? could she not be weakening? could we not be weakening? could you not be weakening? could they not be weakening?
Perfect
could I not have weakened? could you not have weakened? could she not have weakened? could we not have weakened? could you not have weakened? could they not have weakened?
V-ing perfect
could I not have been weakening? could you not have been weakening? could she not have been weakening? could we not have been weakening? could you not have been weakening? could they not have been weakening?