I must challenge you must challenge he must challenge we must challenge you must challenge they must challenge
V-ing form
I must be challenging you must be challenging he must be challenging we must be challenging you must be challenging they must be challenging
Perfect
I must have challenged you must have challenged he must have challenged we must have challenged you must have challenged they must have challenged
V-ing perfect
I must have been challenging you must have been challenging he must have been challenging we must have been challenging you must have been challenging they must have been challenging
Negation
Simple form
I must not challenge you must not challenge he must not challenge we must not challenge you must not challenge they must not challenge
V-ing form
I must not be challenging you must not be challenging he must not be challenging we must not be challenging you must not be challenging they must not be challenging
Perfect
I must not have challenged you must not have challenged he must not have challenged we must not have challenged you must not have challenged they must not have challenged
V-ing perfect
I must not have been challenging you must not have been challenging he must not have been challenging we must not have been challenging you must not have been challenging they must not have been challenging
Interrogative form
Simple form
must I challenge? must you challenge? must he challenge? must we challenge? must you challenge? must they challenge?
V-ing form
must I be challenging? must you be challenging? must he be challenging? must we be challenging? must you be challenging? must they be challenging?
Perfect
must I have challenged? must you have challenged? must he have challenged? must we have challenged? must you have challenged? must they have challenged?
V-ing perfect
must I have been challenging? must you have been challenging? must he have been challenging? must we have been challenging? must you have been challenging? must they have been challenging?
Interro-negative form
Simple form
must I not challenge? must you not challenge? must he not challenge? must we not challenge? must you not challenge? must they not challenge?
V-ing form
must I not be challenging? must you not be challenging? must he not be challenging? must we not be challenging? must you not be challenging? must they not be challenging?
Perfect
must I not have challenged? must you not have challenged? must he not have challenged? must we not have challenged? must you not have challenged? must they not have challenged?
V-ing perfect
must I not have been challenging? must you not have been challenging? must he not have been challenging? must we not have been challenging? must you not have been challenging? must they not have been challenging?