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