I must weaken you must weaken she must weaken we must weaken you must weaken they must weaken
V-ing form
I must be weakening you must be weakening she must be weakening we must be weakening you must be weakening they must be weakening
Perfect
I must have weakened you must have weakened she must have weakened we must have weakened you must have weakened they must have weakened
V-ing perfect
I must have been weakening you must have been weakening she must have been weakening we must have been weakening you must have been weakening they must have been weakening
Negation
Simple form
I mustn't weaken you mustn't weaken she mustn't weaken we mustn't weaken you mustn't weaken they mustn't weaken
V-ing form
I mustn't be weakening you mustn't be weakening she mustn't be weakening we mustn't be weakening you mustn't be weakening they mustn't be weakening
Perfect
I mustn't have weakened you mustn't have weakened she mustn't have weakened we mustn't have weakened you mustn't have weakened they mustn't have weakened
V-ing perfect
I mustn't have been weakening you mustn't have been weakening she mustn't have been weakening we mustn't have been weakening you mustn't have been weakening they mustn't have been weakening
Interrogative form
Simple form
must I weaken? must you weaken? must she weaken? must we weaken? must you weaken? must they weaken?
V-ing form
must I be weakening? must you be weakening? must she be weakening? must we be weakening? must you be weakening? must they be weakening?
Perfect
must I have weakened? must you have weakened? must she have weakened? must we have weakened? must you have weakened? must they have weakened?
V-ing perfect
must I have been weakening? must you have been weakening? must she have been weakening? must we have been weakening? must you have been weakening? must they have been weakening?
Interro-negative form
Simple form
mustn't I weaken? mustn't you weaken? mustn't she weaken? mustn't we weaken? mustn't you weaken? mustn't they weaken?
V-ing form
mustn't I be weakening? mustn't you be weakening? mustn't she be weakening? mustn't we be weakening? mustn't you be weakening? mustn't they be weakening?
Perfect
mustn't I have weakened? mustn't you have weakened? mustn't she have weakened? mustn't we have weakened? mustn't you have weakened? mustn't they have weakened?
V-ing perfect
mustn't I have been weakening? mustn't you have been weakening? mustn't she have been weakening? mustn't we have been weakening? mustn't you have been weakening? mustn't they have been weakening?