English verb conjugation
MUST TOUGHEN

Regular verb: toughen - toughened - toughened

Affirmation

Simple form	V-ing form
I must toughen you must toughen he must toughen we must toughen you must toughen they must toughen	I must be toughening you must be toughening he must be toughening we must be toughening you must be toughening they must be toughening
Perfect	V-ing perfect
I must have toughened you must have toughened he must have toughened we must have toughened you must have toughened they must have toughened	I must have been toughening you must have been toughening he must have been toughening we must have been toughening you must have been toughening they must have been toughening

Negation

Simple form	V-ing form
I must not toughen you must not toughen he must not toughen we must not toughen you must not toughen they must not toughen	I must not be toughening you must not be toughening he must not be toughening we must not be toughening you must not be toughening they must not be toughening
Perfect	V-ing perfect
I must not have toughened you must not have toughened he must not have toughened we must not have toughened you must not have toughened they must not have toughened	I must not have been toughening you must not have been toughening he must not have been toughening we must not have been toughening you must not have been toughening they must not have been toughening

Interrogative form

Simple form	V-ing form
must I toughen? must you toughen? must he toughen? must we toughen? must you toughen? must they toughen?	must I be toughening? must you be toughening? must he be toughening? must we be toughening? must you be toughening? must they be toughening?
Perfect	V-ing perfect
must I have toughened? must you have toughened? must he have toughened? must we have toughened? must you have toughened? must they have toughened?	must I have been toughening? must you have been toughening? must he have been toughening? must we have been toughening? must you have been toughening? must they have been toughening?

Interro-negative form

Simple form	V-ing form
must I not toughen? must you not toughen? must he not toughen? must we not toughen? must you not toughen? must they not toughen?	must I not be toughening? must you not be toughening? must he not be toughening? must we not be toughening? must you not be toughening? must they not be toughening?
Perfect	V-ing perfect
must I not have toughened? must you not have toughened? must he not have toughened? must we not have toughened? must you not have toughened? must they not have toughened?	must I not have been toughening? must you not have been toughening? must he not have been toughening? must we not have been toughening? must you not have been toughening? must they not have been toughening?