What is a good response to an interview question like “Why do you want to work for us?” (a Recovery Center)

It’s for a Drug and Alcohol Recovery Center. I have a job interview coming up.
To be more specific, it’s for an Editorial Assistant. General duties include: editorial research & fact checking, manuscript reader/ evaluator, light graphic design. Working knowledge of grammatical principles, proofreader’s marks & graphic design programs pref’d.

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