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 must not spring you must not spring he must not spring we must not spring you must not spring they must not spring
V-ing form
I must not be springing you must not be springing he must not be springing we must not be springing you must not be springing they must not be springing
Perfect
I must not have sprung you must not have sprung he must not have sprung we must not have sprung you must not have sprung they must not have sprung
V-ing perfect
I must not have been springing you must not have been springing he must not have been springing we must not have been springing you must not have been springing they must not 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
must I not spring? must you not spring? must he not spring? must we not spring? must you not spring? must they not spring?
V-ing form
must I not be springing? must you not be springing? must he not be springing? must we not be springing? must you not be springing? must they not be springing?
Perfect
must I not have sprung? must you not have sprung? must he not have sprung? must we not have sprung? must you not have sprung? must they not have sprung?
V-ing perfect
must I not have been springing? must you not have been springing? must he not have been springing? must we not have been springing? must you not have been springing? must they not have been springing?