Shenzhou X and three astronauts  were sent up from Jiuquan Satellite Launch Center, Gansu province, into a clear blue sky on Tuesday, bringing the nation one step closer to building its own space  station in 2020. Two men, mission commander  Nie Haisheng and Zhang Xiaoguang, and China's second female astronaut, Wang Yaping, are expected to stay in space for 15 days. They will teach young people about science and do two _ , between Shenzhou X and the unmanned Tiangong-1 space module, a technically difficult procedure that brings two spaceship together in high-speed orbit . The trip is our country's fifth manned space mission, 10 years after the country's first astronaut, Yang Liwei, went into space in 2003. How long will they stay in space?
About a week About two weeks About a month About two months