I must labour you must labour she must labour we must labour you must labour they must labour
V-ing form
I must be labouring you must be labouring she must be labouring we must be labouring you must be labouring they must be labouring
Perfect
I must have laboured you must have laboured she must have laboured we must have laboured you must have laboured they must have laboured
V-ing perfect
I must have been labouring you must have been labouring she must have been labouring we must have been labouring you must have been labouring they must have been labouring
Negation
Simple form
I must not labour you must not labour she must not labour we must not labour you must not labour they must not labour
V-ing form
I must not be labouring you must not be labouring she must not be labouring we must not be labouring you must not be labouring they must not be labouring
Perfect
I must not have laboured you must not have laboured she must not have laboured we must not have laboured you must not have laboured they must not have laboured
V-ing perfect
I must not have been labouring you must not have been labouring she must not have been labouring we must not have been labouring you must not have been labouring they must not have been labouring
Interrogative form
Simple form
must I labour? must you labour? must she labour? must we labour? must you labour? must they labour?
V-ing form
must I be labouring? must you be labouring? must she be labouring? must we be labouring? must you be labouring? must they be labouring?
Perfect
must I have laboured? must you have laboured? must she have laboured? must we have laboured? must you have laboured? must they have laboured?
V-ing perfect
must I have been labouring? must you have been labouring? must she have been labouring? must we have been labouring? must you have been labouring? must they have been labouring?
Interro-negative form
Simple form
must I not labour? must you not labour? must she not labour? must we not labour? must you not labour? must they not labour?
V-ing form
must I not be labouring? must you not be labouring? must she not be labouring? must we not be labouring? must you not be labouring? must they not be labouring?
Perfect
must I not have laboured? must you not have laboured? must she not have laboured? must we not have laboured? must you not have laboured? must they not have laboured?
V-ing perfect
must I not have been labouring? must you not have been labouring? must she not have been labouring? must we not have been labouring? must you not have been labouring? must they not have been labouring?