There are 23 helping verbs in the English language. It cannot stand alone as a verb, it must *help *another one already in the sentence, hence the name. All of the verbs you listed are helping verbs.
All the listed verbs (must, can, would, be) are helping verbs. Each assists the main verb in conveying mood, tense, or voice. Therefore, none of the options is not a helping verb.
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