Yo trabajo por horas. a. muchos b. mucho c. mucha d. muchas

The correct Article to fill the blank in the sentence is:

Many of the articles in Spanish have gender and number characteristics that must agree with the noun to which it refers, in the case of the form "mucho" they are usually distinguished as follows:

Since the noun "horas" has female gender and its number is plural, an article with those same characteristics is used, which, based on the guide above, is "muchas."

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