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