I must discuss you must discuss he must discuss we must discuss you must discuss they must discuss
V-ing form
I must be discussing you must be discussing he must be discussing we must be discussing you must be discussing they must be discussing
Perfect
I must have discussed you must have discussed he must have discussed we must have discussed you must have discussed they must have discussed
V-ing perfect
I must have been discussing you must have been discussing he must have been discussing we must have been discussing you must have been discussing they must have been discussing
Negation
Simple form
I must not discuss you must not discuss he must not discuss we must not discuss you must not discuss they must not discuss
V-ing form
I must not be discussing you must not be discussing he must not be discussing we must not be discussing you must not be discussing they must not be discussing
Perfect
I must not have discussed you must not have discussed he must not have discussed we must not have discussed you must not have discussed they must not have discussed
V-ing perfect
I must not have been discussing you must not have been discussing he must not have been discussing we must not have been discussing you must not have been discussing they must not have been discussing
Interrogative form
Simple form
must I discuss? must you discuss? must he discuss? must we discuss? must you discuss? must they discuss?
V-ing form
must I be discussing? must you be discussing? must he be discussing? must we be discussing? must you be discussing? must they be discussing?
Perfect
must I have discussed? must you have discussed? must he have discussed? must we have discussed? must you have discussed? must they have discussed?
V-ing perfect
must I have been discussing? must you have been discussing? must he have been discussing? must we have been discussing? must you have been discussing? must they have been discussing?
Interro-negative form
Simple form
must I not discuss? must you not discuss? must he not discuss? must we not discuss? must you not discuss? must they not discuss?
V-ing form
must I not be discussing? must you not be discussing? must he not be discussing? must we not be discussing? must you not be discussing? must they not be discussing?
Perfect
must I not have discussed? must you not have discussed? must he not have discussed? must we not have discussed? must you not have discussed? must they not have discussed?
V-ing perfect
must I not have been discussing? must you not have been discussing? must he not have been discussing? must we not have been discussing? must you not have been discussing? must they not have been discussing?