I must discuss you must discuss she must discuss we must discuss you must discuss they must discuss
V-ing form
I must be discussing you must be discussing she must be discussing we must be discussing you must be discussing they must be discussing
Perfect
I must have discussed you must have discussed she 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 she must have been discussing we must have been discussing you must have been discussing they must have been discussing
Negation
Simple form
I mustn't discuss you mustn't discuss she mustn't discuss we mustn't discuss you mustn't discuss they mustn't discuss
V-ing form
I mustn't be discussing you mustn't be discussing she mustn't be discussing we mustn't be discussing you mustn't be discussing they mustn't be discussing
Perfect
I mustn't have discussed you mustn't have discussed she mustn't have discussed we mustn't have discussed you mustn't have discussed they mustn't have discussed
V-ing perfect
I mustn't have been discussing you mustn't have been discussing she mustn't have been discussing we mustn't have been discussing you mustn't have been discussing they mustn't have been discussing
Interrogative form
Simple form
must I discuss? must you discuss? must she discuss? must we discuss? must you discuss? must they discuss?
V-ing form
must I be discussing? must you be discussing? must she be discussing? must we be discussing? must you be discussing? must they be discussing?
Perfect
must I have discussed? must you have discussed? must she 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 she have been discussing? must we have been discussing? must you have been discussing? must they have been discussing?
Interro-negative form
Simple form
mustn't I discuss? mustn't you discuss? mustn't she discuss? mustn't we discuss? mustn't you discuss? mustn't they discuss?
V-ing form
mustn't I be discussing? mustn't you be discussing? mustn't she be discussing? mustn't we be discussing? mustn't you be discussing? mustn't they be discussing?
Perfect
mustn't I have discussed? mustn't you have discussed? mustn't she have discussed? mustn't we have discussed? mustn't you have discussed? mustn't they have discussed?
V-ing perfect
mustn't I have been discussing? mustn't you have been discussing? mustn't she have been discussing? mustn't we have been discussing? mustn't you have been discussing? mustn't they have been discussing?