I must lighten you must lighten he must lighten we must lighten you must lighten they must lighten
V-ing form
I must be lightening you must be lightening he must be lightening we must be lightening you must be lightening they must be lightening
Perfect
I must have lightened you must have lightened he 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 he must have been lightening we must have been lightening you must have been lightening they must have been lightening
Negation
Simple form
I must not lighten you must not lighten he must not lighten we must not lighten you must not lighten they must not lighten
V-ing form
I must not be lightening you must not be lightening he must not be lightening we must not be lightening you must not be lightening they must not be lightening
Perfect
I must not have lightened you must not have lightened he must not have lightened we must not have lightened you must not have lightened they must not have lightened
V-ing perfect
I must not have been lightening you must not have been lightening he must not have been lightening we must not have been lightening you must not have been lightening they must not have been lightening
Interrogative form
Simple form
must I lighten? must you lighten? must he lighten? must we lighten? must you lighten? must they lighten?
V-ing form
must I be lightening? must you be lightening? must he be lightening? must we be lightening? must you be lightening? must they be lightening?
Perfect
must I have lightened? must you have lightened? must he 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 he have been lightening? must we have been lightening? must you have been lightening? must they have been lightening?
Interro-negative form
Simple form
must I not lighten? must you not lighten? must he not lighten? must we not lighten? must you not lighten? must they not lighten?
V-ing form
must I not be lightening? must you not be lightening? must he not be lightening? must we not be lightening? must you not be lightening? must they not be lightening?
Perfect
must I not have lightened? must you not have lightened? must he not have lightened? must we not have lightened? must you not have lightened? must they not have lightened?
V-ing perfect
must I not have been lightening? must you not have been lightening? must he not have been lightening? must we not have been lightening? must you not have been lightening? must they not have been lightening?