English verb conjugation
MUST STRENGTHEN

Regular verb: strengthen - strengthened - strengthened

Affirmation

Simple form	V-ing form
I must strengthen you must strengthen he must strengthen we must strengthen you must strengthen they must strengthen	I must be strengthening you must be strengthening he must be strengthening we must be strengthening you must be strengthening they must be strengthening
Perfect	V-ing perfect
I must have strengthened you must have strengthened he must have strengthened we must have strengthened you must have strengthened they must have strengthened	I must have been strengthening you must have been strengthening he must have been strengthening we must have been strengthening you must have been strengthening they must have been strengthening

Negation

Simple form	V-ing form
I mustn't strengthen you mustn't strengthen he mustn't strengthen we mustn't strengthen you mustn't strengthen they mustn't strengthen	I mustn't be strengthening you mustn't be strengthening he mustn't be strengthening we mustn't be strengthening you mustn't be strengthening they mustn't be strengthening
Perfect	V-ing perfect
I mustn't have strengthened you mustn't have strengthened he mustn't have strengthened we mustn't have strengthened you mustn't have strengthened they mustn't have strengthened	I mustn't have been strengthening you mustn't have been strengthening he mustn't have been strengthening we mustn't have been strengthening you mustn't have been strengthening they mustn't have been strengthening

Interrogative form

Simple form	V-ing form
must I strengthen? must you strengthen? must he strengthen? must we strengthen? must you strengthen? must they strengthen?	must I be strengthening? must you be strengthening? must he be strengthening? must we be strengthening? must you be strengthening? must they be strengthening?
Perfect	V-ing perfect
must I have strengthened? must you have strengthened? must he have strengthened? must we have strengthened? must you have strengthened? must they have strengthened?	must I have been strengthening? must you have been strengthening? must he have been strengthening? must we have been strengthening? must you have been strengthening? must they have been strengthening?

Interro-negative form

Simple form	V-ing form
mustn't I strengthen? mustn't you strengthen? mustn't he strengthen? mustn't we strengthen? mustn't you strengthen? mustn't they strengthen?	mustn't I be strengthening? mustn't you be strengthening? mustn't he be strengthening? mustn't we be strengthening? mustn't you be strengthening? mustn't they be strengthening?
Perfect	V-ing perfect
mustn't I have strengthened? mustn't you have strengthened? mustn't he have strengthened? mustn't we have strengthened? mustn't you have strengthened? mustn't they have strengthened?	mustn't I have been strengthening? mustn't you have been strengthening? mustn't he have been strengthening? mustn't we have been strengthening? mustn't you have been strengthening? mustn't they have been strengthening?