I must background you must background he must background we must background you must background they must background
V-ing form
I must be backgrounding you must be backgrounding he must be backgrounding we must be backgrounding you must be backgrounding they must be backgrounding
Perfect
I must have backgrounded you must have backgrounded he must have backgrounded we must have backgrounded you must have backgrounded they must have backgrounded
V-ing perfect
I must have been backgrounding you must have been backgrounding he must have been backgrounding we must have been backgrounding you must have been backgrounding they must have been backgrounding
Negation
Simple form
I must not background you must not background he must not background we must not background you must not background they must not background
V-ing form
I must not be backgrounding you must not be backgrounding he must not be backgrounding we must not be backgrounding you must not be backgrounding they must not be backgrounding
Perfect
I must not have backgrounded you must not have backgrounded he must not have backgrounded we must not have backgrounded you must not have backgrounded they must not have backgrounded
V-ing perfect
I must not have been backgrounding you must not have been backgrounding he must not have been backgrounding we must not have been backgrounding you must not have been backgrounding they must not have been backgrounding
Interrogative form
Simple form
must I background? must you background? must he background? must we background? must you background? must they background?
V-ing form
must I be backgrounding? must you be backgrounding? must he be backgrounding? must we be backgrounding? must you be backgrounding? must they be backgrounding?
Perfect
must I have backgrounded? must you have backgrounded? must he have backgrounded? must we have backgrounded? must you have backgrounded? must they have backgrounded?
V-ing perfect
must I have been backgrounding? must you have been backgrounding? must he have been backgrounding? must we have been backgrounding? must you have been backgrounding? must they have been backgrounding?
Interro-negative form
Simple form
must I not background? must you not background? must he not background? must we not background? must you not background? must they not background?
V-ing form
must I not be backgrounding? must you not be backgrounding? must he not be backgrounding? must we not be backgrounding? must you not be backgrounding? must they not be backgrounding?
Perfect
must I not have backgrounded? must you not have backgrounded? must he not have backgrounded? must we not have backgrounded? must you not have backgrounded? must they not have backgrounded?
V-ing perfect
must I not have been backgrounding? must you not have been backgrounding? must he not have been backgrounding? must we not have been backgrounding? must you not have been backgrounding? must they not have been backgrounding?