I must frighten you must frighten she must frighten we must frighten you must frighten they must frighten
V-ing form
I must be frightening you must be frightening she must be frightening we must be frightening you must be frightening they must be frightening
Perfect
I must have frightened you must have frightened she must have frightened we must have frightened you must have frightened they must have frightened
V-ing perfect
I must have been frightening you must have been frightening she must have been frightening we must have been frightening you must have been frightening they must have been frightening
Negation
Simple form
I must not frighten you must not frighten she must not frighten we must not frighten you must not frighten they must not frighten
V-ing form
I must not be frightening you must not be frightening she must not be frightening we must not be frightening you must not be frightening they must not be frightening
Perfect
I must not have frightened you must not have frightened she must not have frightened we must not have frightened you must not have frightened they must not have frightened
V-ing perfect
I must not have been frightening you must not have been frightening she must not have been frightening we must not have been frightening you must not have been frightening they must not have been frightening
Interrogative form
Simple form
must I frighten? must you frighten? must she frighten? must we frighten? must you frighten? must they frighten?
V-ing form
must I be frightening? must you be frightening? must she be frightening? must we be frightening? must you be frightening? must they be frightening?
Perfect
must I have frightened? must you have frightened? must she have frightened? must we have frightened? must you have frightened? must they have frightened?
V-ing perfect
must I have been frightening? must you have been frightening? must she have been frightening? must we have been frightening? must you have been frightening? must they have been frightening?
Interro-negative form
Simple form
must I not frighten? must you not frighten? must she not frighten? must we not frighten? must you not frighten? must they not frighten?
V-ing form
must I not be frightening? must you not be frightening? must she not be frightening? must we not be frightening? must you not be frightening? must they not be frightening?
Perfect
must I not have frightened? must you not have frightened? must she not have frightened? must we not have frightened? must you not have frightened? must they not have frightened?
V-ing perfect
must I not have been frightening? must you not have been frightening? must she not have been frightening? must we not have been frightening? must you not have been frightening? must they not have been frightening?