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