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