I must guess you must guess she must guess we must guess you must guess they must guess
V-ing form
I must be guessing you must be guessing she must be guessing we must be guessing you must be guessing they must be guessing
Perfect
I must have guessed you must have guessed she must have guessed we must have guessed you must have guessed they must have guessed
V-ing perfect
I must have been guessing you must have been guessing she must have been guessing we must have been guessing you must have been guessing they must have been guessing
Negation
Simple form
I must not guess you must not guess she must not guess we must not guess you must not guess they must not guess
V-ing form
I must not be guessing you must not be guessing she must not be guessing we must not be guessing you must not be guessing they must not be guessing
Perfect
I must not have guessed you must not have guessed she must not have guessed we must not have guessed you must not have guessed they must not have guessed
V-ing perfect
I must not have been guessing you must not have been guessing she must not have been guessing we must not have been guessing you must not have been guessing they must not have been guessing
Interrogative form
Simple form
must I guess? must you guess? must she guess? must we guess? must you guess? must they guess?
V-ing form
must I be guessing? must you be guessing? must she be guessing? must we be guessing? must you be guessing? must they be guessing?
Perfect
must I have guessed? must you have guessed? must she have guessed? must we have guessed? must you have guessed? must they have guessed?
V-ing perfect
must I have been guessing? must you have been guessing? must she have been guessing? must we have been guessing? must you have been guessing? must they have been guessing?
Interro-negative form
Simple form
must I not guess? must you not guess? must she not guess? must we not guess? must you not guess? must they not guess?
V-ing form
must I not be guessing? must you not be guessing? must she not be guessing? must we not be guessing? must you not be guessing? must they not be guessing?
Perfect
must I not have guessed? must you not have guessed? must she not have guessed? must we not have guessed? must you not have guessed? must they not have guessed?
V-ing perfect
must I not have been guessing? must you not have been guessing? must she not have been guessing? must we not have been guessing? must you not have been guessing? must they not have been guessing?