I must decay you must decay he must decay we must decay you must decay they must decay
V-ing form
I must be decaying you must be decaying he must be decaying we must be decaying you must be decaying they must be decaying
Perfect
I must have decayed you must have decayed he must have decayed we must have decayed you must have decayed they must have decayed
V-ing perfect
I must have been decaying you must have been decaying he must have been decaying we must have been decaying you must have been decaying they must have been decaying
Negation
Simple form
I must not decay you must not decay he must not decay we must not decay you must not decay they must not decay
V-ing form
I must not be decaying you must not be decaying he must not be decaying we must not be decaying you must not be decaying they must not be decaying
Perfect
I must not have decayed you must not have decayed he must not have decayed we must not have decayed you must not have decayed they must not have decayed
V-ing perfect
I must not have been decaying you must not have been decaying he must not have been decaying we must not have been decaying you must not have been decaying they must not have been decaying
Interrogative form
Simple form
must I decay? must you decay? must he decay? must we decay? must you decay? must they decay?
V-ing form
must I be decaying? must you be decaying? must he be decaying? must we be decaying? must you be decaying? must they be decaying?
Perfect
must I have decayed? must you have decayed? must he have decayed? must we have decayed? must you have decayed? must they have decayed?
V-ing perfect
must I have been decaying? must you have been decaying? must he have been decaying? must we have been decaying? must you have been decaying? must they have been decaying?
Interro-negative form
Simple form
must I not decay? must you not decay? must he not decay? must we not decay? must you not decay? must they not decay?
V-ing form
must I not be decaying? must you not be decaying? must he not be decaying? must we not be decaying? must you not be decaying? must they not be decaying?
Perfect
must I not have decayed? must you not have decayed? must he not have decayed? must we not have decayed? must you not have decayed? must they not have decayed?
V-ing perfect
must I not have been decaying? must you not have been decaying? must he not have been decaying? must we not have been decaying? must you not have been decaying? must they not have been decaying?