According to the text, Bento Boxes is a/ an.

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Bento boxes

    People in offices in Japan often have a bento at lunchtime. They do not eat a meal in a restaurant; they eat a bento in the office. They regularly have a menu for the bentos in the office and they telephone a bento store with their orders. The people at bento store make the bentos and take them to all the offices at about 12p.m.