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