Answer:
All astronauts who visit the International Space Station (ISS) must learn Russian. This is because the ISS is a joint venture between several different countries, including the United States and Russia. Russian is the official language of the ISS, and all communication between astronauts and mission control is conducted in Russian. Additionally, many of the systems and controls on the ISS are labeled in Russian, so astronauts must be able to read and understand Russian in order to operate them safely. Learning Russian is an essential part of the training process for astronauts who plan to visit the ISS.