I must substitute you must substitute she must substitute we must substitute you must substitute they must substitute
V-ing form
I must be substituting you must be substituting she must be substituting we must be substituting you must be substituting they must be substituting
Perfect
I must have substituted you must have substituted she must have substituted we must have substituted you must have substituted they must have substituted
V-ing perfect
I must have been substituting you must have been substituting she must have been substituting we must have been substituting you must have been substituting they must have been substituting
Negation
Simple form
I mustn't substitute you mustn't substitute she mustn't substitute we mustn't substitute you mustn't substitute they mustn't substitute
V-ing form
I mustn't be substituting you mustn't be substituting she mustn't be substituting we mustn't be substituting you mustn't be substituting they mustn't be substituting
Perfect
I mustn't have substituted you mustn't have substituted she mustn't have substituted we mustn't have substituted you mustn't have substituted they mustn't have substituted
V-ing perfect
I mustn't have been substituting you mustn't have been substituting she mustn't have been substituting we mustn't have been substituting you mustn't have been substituting they mustn't have been substituting
Interrogative form
Simple form
must I substitute? must you substitute? must she substitute? must we substitute? must you substitute? must they substitute?
V-ing form
must I be substituting? must you be substituting? must she be substituting? must we be substituting? must you be substituting? must they be substituting?
Perfect
must I have substituted? must you have substituted? must she have substituted? must we have substituted? must you have substituted? must they have substituted?
V-ing perfect
must I have been substituting? must you have been substituting? must she have been substituting? must we have been substituting? must you have been substituting? must they have been substituting?
Interro-negative form
Simple form
mustn't I substitute? mustn't you substitute? mustn't she substitute? mustn't we substitute? mustn't you substitute? mustn't they substitute?
V-ing form
mustn't I be substituting? mustn't you be substituting? mustn't she be substituting? mustn't we be substituting? mustn't you be substituting? mustn't they be substituting?
Perfect
mustn't I have substituted? mustn't you have substituted? mustn't she have substituted? mustn't we have substituted? mustn't you have substituted? mustn't they have substituted?
V-ing perfect
mustn't I have been substituting? mustn't you have been substituting? mustn't she have been substituting? mustn't we have been substituting? mustn't you have been substituting? mustn't they have been substituting?