I must litter you must litter he must litter we must litter you must litter they must litter
V-ing form
I must be littering you must be littering he must be littering we must be littering you must be littering they must be littering
Perfect
I must have littered you must have littered he must have littered we must have littered you must have littered they must have littered
V-ing perfect
I must have been littering you must have been littering he must have been littering we must have been littering you must have been littering they must have been littering
Negation
Simple form
I must not litter you must not litter he must not litter we must not litter you must not litter they must not litter
V-ing form
I must not be littering you must not be littering he must not be littering we must not be littering you must not be littering they must not be littering
Perfect
I must not have littered you must not have littered he must not have littered we must not have littered you must not have littered they must not have littered
V-ing perfect
I must not have been littering you must not have been littering he must not have been littering we must not have been littering you must not have been littering they must not have been littering
Interrogative form
Simple form
must I litter? must you litter? must he litter? must we litter? must you litter? must they litter?
V-ing form
must I be littering? must you be littering? must he be littering? must we be littering? must you be littering? must they be littering?
Perfect
must I have littered? must you have littered? must he have littered? must we have littered? must you have littered? must they have littered?
V-ing perfect
must I have been littering? must you have been littering? must he have been littering? must we have been littering? must you have been littering? must they have been littering?
Interro-negative form
Simple form
must I not litter? must you not litter? must he not litter? must we not litter? must you not litter? must they not litter?
V-ing form
must I not be littering? must you not be littering? must he not be littering? must we not be littering? must you not be littering? must they not be littering?
Perfect
must I not have littered? must you not have littered? must he not have littered? must we not have littered? must you not have littered? must they not have littered?
V-ing perfect
must I not have been littering? must you not have been littering? must he not have been littering? must we not have been littering? must you not have been littering? must they not have been littering?