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