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