I must lower you must lower he must lower we must lower you must lower they must lower
V-ing form
I must be lowering you must be lowering he must be lowering we must be lowering you must be lowering they must be lowering
Perfect
I must have lowered you must have lowered he must have lowered we must have lowered you must have lowered they must have lowered
V-ing perfect
I must have been lowering you must have been lowering he must have been lowering we must have been lowering you must have been lowering they must have been lowering
Negation
Simple form
I mustn't lower you mustn't lower he mustn't lower we mustn't lower you mustn't lower they mustn't lower
V-ing form
I mustn't be lowering you mustn't be lowering he mustn't be lowering we mustn't be lowering you mustn't be lowering they mustn't be lowering
Perfect
I mustn't have lowered you mustn't have lowered he mustn't have lowered we mustn't have lowered you mustn't have lowered they mustn't have lowered
V-ing perfect
I mustn't have been lowering you mustn't have been lowering he mustn't have been lowering we mustn't have been lowering you mustn't have been lowering they mustn't have been lowering
Interrogative form
Simple form
must I lower? must you lower? must he lower? must we lower? must you lower? must they lower?
V-ing form
must I be lowering? must you be lowering? must he be lowering? must we be lowering? must you be lowering? must they be lowering?
Perfect
must I have lowered? must you have lowered? must he have lowered? must we have lowered? must you have lowered? must they have lowered?
V-ing perfect
must I have been lowering? must you have been lowering? must he have been lowering? must we have been lowering? must you have been lowering? must they have been lowering?
Interro-negative form
Simple form
mustn't I lower? mustn't you lower? mustn't he lower? mustn't we lower? mustn't you lower? mustn't they lower?
V-ing form
mustn't I be lowering? mustn't you be lowering? mustn't he be lowering? mustn't we be lowering? mustn't you be lowering? mustn't they be lowering?
Perfect
mustn't I have lowered? mustn't you have lowered? mustn't he have lowered? mustn't we have lowered? mustn't you have lowered? mustn't they have lowered?
V-ing perfect
mustn't I have been lowering? mustn't you have been lowering? mustn't he have been lowering? mustn't we have been lowering? mustn't you have been lowering? mustn't they have been lowering?