[Answer] All astronauts who visit the International Space Station must learn what language?

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All astronauts who visit the International Space Station must learn what language?

• Russian:English is the official language aboard the International Space Station. Nevertheless, all astronauts traveling to the ISS are also required to learn to speak Russian. Since the end of NASA’s Space Shuttle program in 2011, the only way to reach the International Space Station is via a Russian Soyuz spacecraft. And because all its controls are in Russian, every astronaut is required to master the language. Astronauts undergo hundreds of hours of Russian lessons in order to achieve the minimum level of fluency; many astronauts claim this is the most difficult aspect of their training.

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