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 must not strengthen you must not strengthen he must not strengthen we must not strengthen you must not strengthen they must not strengthen	I must not be strengthening you must not be strengthening he must not be strengthening we must not be strengthening you must not be strengthening they must not be strengthening
Perfect	V-ing perfect
I must not have strengthened you must not have strengthened he must not have strengthened we must not have strengthened you must not have strengthened they must not have strengthened	I must not have been strengthening you must not have been strengthening he must not have been strengthening we must not have been strengthening you must not have been strengthening they must not 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
must I not strengthen? must you not strengthen? must he not strengthen? must we not strengthen? must you not strengthen? must they not strengthen?	must I not be strengthening? must you not be strengthening? must he not be strengthening? must we not be strengthening? must you not be strengthening? must they not be strengthening?
Perfect	V-ing perfect
must I not have strengthened? must you not have strengthened? must he not have strengthened? must we not have strengthened? must you not have strengthened? must they not have strengthened?	must I not have been strengthening? must you not have been strengthening? must he not have been strengthening? must we not have been strengthening? must you not have been strengthening? must they not have been strengthening?