A、250. B、340. C、430. D、520. D新闻中提到，Kelly是美国空间飞行时间最长的纪录保持者，完成4次任务，在空间站中驻留了520天。

　　Scott Kelly and Mikhail Kornienko have their feet on the ground for the first time in 340 days. Riding in a Russian spacecraft, they made it back to Kazakhstan, along with a fellow Russian cosmonaut. Theirs was a record-setting journey. It is the longest time humans have spent living on the International Space Station (ISS). (3) Now, Kelly also holds the record for the longest time an American has spent in space: 520 days in space, over four missions. (4) After being taken out of the capsule (太空舱), they were put in special chairs while they start getting used to Earth’s gravity again. They were to be examined and tested before Kelly is flown home to the United States. After undergoing more tests and exams at NASA’s Houston, Texas offices, Kelly said he wanted to go home and jump into his swimming pool.       3. How many days has Kelly spent in space?
　　4. Why were Kelly and Kornienko put in special chairs?