Answer:
Will
Step-by-step explanation:
Helping verbs (also “auxiliary verbs”) are those that do not have meaning of their own as its function is to help the main verb of a sentence to express a tense (i.e past, present or future), expectation, probability, obligation, potential, directions, and others. The word “will” is one of the few helping verbs that exist and is used to form future tenses, make requests or offers, express willingness or ability, express likelihood, or in conditional sentences and commands.
In the sentence “How many tacos will you eat?,” the helping verb “will” is used to help the verb form the future tense.