Which of the following is an international firm?

Walmart Inc. is recognized as an international firm due to its extensive global footprint and operations in numerous countries outside the United States. It operates thousands of retail stores in multiple formats around the world, including supercenters, discount stores, and warehouse clubs. This widespread presence allows Walmart to adapt to various international markets and meet diverse consumer needs, thus reinforcing its status as a multinational corporation.

The other businesses listed may be successful domestically but do not operate on a significant international scale. For instance, a company like Sunrise Computer Systems might focus on the local or national market, while Gary's Gas Station is likely a local business serving a specific community. Buer's Brewers also seems to be limited in its operations to a specific region. Their lack of international operations differentiates them from Walmart, underscoring the defining characteristic of an international firm as one that engages in business across national borders.