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