I must retard you must retard he must retard we must retard you must retard they must retard
V-ing form
I must be retarding you must be retarding he must be retarding we must be retarding you must be retarding they must be retarding
Perfect
I must have retarded you must have retarded he must have retarded we must have retarded you must have retarded they must have retarded
V-ing perfect
I must have been retarding you must have been retarding he must have been retarding we must have been retarding you must have been retarding they must have been retarding
Negation
Simple form
I must not retard you must not retard he must not retard we must not retard you must not retard they must not retard
V-ing form
I must not be retarding you must not be retarding he must not be retarding we must not be retarding you must not be retarding they must not be retarding
Perfect
I must not have retarded you must not have retarded he must not have retarded we must not have retarded you must not have retarded they must not have retarded
V-ing perfect
I must not have been retarding you must not have been retarding he must not have been retarding we must not have been retarding you must not have been retarding they must not have been retarding
Interrogative form
Simple form
must I retard? must you retard? must he retard? must we retard? must you retard? must they retard?
V-ing form
must I be retarding? must you be retarding? must he be retarding? must we be retarding? must you be retarding? must they be retarding?
Perfect
must I have retarded? must you have retarded? must he have retarded? must we have retarded? must you have retarded? must they have retarded?
V-ing perfect
must I have been retarding? must you have been retarding? must he have been retarding? must we have been retarding? must you have been retarding? must they have been retarding?
Interro-negative form
Simple form
must I not retard? must you not retard? must he not retard? must we not retard? must you not retard? must they not retard?
V-ing form
must I not be retarding? must you not be retarding? must he not be retarding? must we not be retarding? must you not be retarding? must they not be retarding?
Perfect
must I not have retarded? must you not have retarded? must he not have retarded? must we not have retarded? must you not have retarded? must they not have retarded?
V-ing perfect
must I not have been retarding? must you not have been retarding? must he not have been retarding? must we not have been retarding? must you not have been retarding? must they not have been retarding?