Three astronauts returned to Earth safely on Wednesday after a successful 15-day mission  , marking another step forward towards the country's goal of building a manned space station by 2020. Zhang Youxia, commander-in-chief of China's manned space program, said the Shenzhou X mission was a "complete success". The Shenzhou X landed safely in north China's Inner Mongolia Autonomous Region at about 8:07 a.m. on June 26, 2013. All three astronauts were in good physical condition. Nie Haisheng, commander of the Shenzhou X crew and a second-time space traveler, was the first to get out of the bowl-like module , followed by Wang Yaping, the only female astronaut of the mission, and Zhang Xiaoguang. During a brief welcoming ceremony held at the landing area, the astronauts waved happily to a crowd consisting of officers, the search and recovery team, and health personnel. "It feels really good to be back home," said astronaut Nie Haisheng. "We are dreamers, and we have now realized our dream," said Zhang Xiaoguang. "Our space dream knows no limit, and our hard work will never stop," he said. Compared with its previous mission Shenzhou IX last year, the Shenzhou X is no longer experimental but considered an applicable shuttle system for sending astronauts and supplies to orbiting modules. The mission aims to further test technologies designed for docking and supporting astronauts' stay in space, as well as to use new technologies related to the construction of a space station. In its 15-day journey in space, Shenzhou X docked with the orbiting space lab Tiangong-1 twice, once through automatic operation and the other manual .The Tiangong-1 space lab has been in orbit for more than 600 days. It's designed to work for two years. The module is considered the first step in building a permanent space station in the future. And the astronauts spent 12 days in Tiangong-1, where they conducted space medical experiments, technical tests and gave a science lesson to students on Earth on June 19 about basic physics principles. The lecture was the second video class sent from space, with US astronaut Barbara Morgan's 25-minute class being the first in 2007. China is the third country after the United States and Russia to acquire the technologies and skills necessary for space rendezvous and docking procedures, as well as supply manpower and material for an orbiting module via different docking methods. Previous docking procedures conducted between Shenzhou-type spacecraft and the orbiting space lab included two automated dockings by the unmanned Shenzhou-8 in 2011 and both an automated and manual docking by the manned Shenzhou-9 in 2012. Since its first manned space space mission in 2003, China has sent ten astronauts and six spacecrafts into the space. According to the passage, the Shenzhou X   _  .
was sent into space on June 11, 2013 is still an experimental shuttle system sent many supplies to the manned space station returned to Earth safely on the afternoon of June 26
Question: Three astronauts returned to Earth safely on Wednesday after a successful 15-day mission  , marking another step forward towards the country's goal of building a manned space station by 2020. Zhang Youxia, commander-in-chief of China's manned space program, said the Shenzhou X mission was a "complete success". The Shenzhou X landed safely in north China's Inner Mongolia Autonomous Region at about 8:07 a.m. on June 26, 2013. All three astronauts were in good physical condition. Nie Haisheng, commander of the Shenzhou X crew and a second-time space traveler, was the first to get out of the bowl-like module , followed by Wang Yaping, the only female astronaut of the mission, and Zhang Xiaoguang. During a brief welcoming ceremony held at the landing area, the astronauts waved happily to a crowd consisting of officers, the search and recovery team, and health personnel. "It feels really good to be back home," said astronaut Nie Haisheng. "We are dreamers, and we have now realized our dream," said Zhang Xiaoguang. "Our space dream knows no limit, and our hard work will never stop," he said. Compared with its previous mission Shenzhou IX last year, the Shenzhou X is no longer experimental but considered an applicable shuttle system for sending astronauts and supplies to orbiting modules. The mission aims to further test technologies designed for docking and supporting astronauts' stay in space, as well as to use new technologies related to the construction of a space station. In its 15-day journey in space, Shenzhou X docked with the orbiting space lab Tiangong-1 twice, once through automatic operation and the other manual .The Tiangong-1 space lab has been in orbit for more than 600 days. It's designed to work for two years. The module is considered the first step in building a permanent space station in the future. And the astronauts spent 12 days in Tiangong-1, where they conducted space medical experiments, technical tests and gave a science lesson to students on Earth on June 19 about basic physics principles. The lecture was the second video class sent from space, with US astronaut Barbara Morgan's 25-minute class being the first in 2007. China is the third country after the United States and Russia to acquire the technologies and skills necessary for space rendezvous and docking procedures, as well as supply manpower and material for an orbiting module via different docking methods. Previous docking procedures conducted between Shenzhou-type spacecraft and the orbiting space lab included two automated dockings by the unmanned Shenzhou-8 in 2011 and both an automated and manual docking by the manned Shenzhou-9 in 2012. Since its first manned space space mission in 2003, China has sent ten astronauts and six spacecrafts into the space. According to the passage, the Shenzhou X   _  .
A. was sent into space on June 11, 2013
B. is still an experimental shuttle system
C. sent many supplies to the manned space station
D. returned to Earth safely on the afternoon of June 26
Answer: