I must decay you must decay she must decay we must decay you must decay they must decay
V-ing form
I must be decaying you must be decaying she must be decaying we must be decaying you must be decaying they must be decaying
Perfect
I must have decayed you must have decayed she 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 she 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 she 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 she 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 she 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 she 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 she decay? must we decay? must you decay? must they decay?
V-ing form
must I be decaying? must you be decaying? must she be decaying? must we be decaying? must you be decaying? must they be decaying?
Perfect
must I have decayed? must you have decayed? must she 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 she 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 she 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 she 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 she 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 she not have been decaying? must we not have been decaying? must you not have been decaying? must they not have been decaying?