The three Chinese astronauts living in space for 90 days have returned to Earth, 【小题1】 (mark) an end to China’s longest-ever crewed mission.

The astronauts—Nie Haisheng, Liu Borning and Tang Hongbo— 【小题2】 (send) in June to the core module (舱) of China’s planned space station, called Tiangong or Heavenly Palace, which is still 【小题3】   construction in a low-Earth orbit.

The crew boarded the Shenzhou-12 spacecraft on Thursday and touched down at the Gobi desert in Inner Mongolia on Friday afternoon, state news agency Xinhua reported.

During their three months at 【小题4】 space station, the astronauts conducted two spacewalks to test their 【小题5】(equip), new-generation spacesuits and life maintenance systems. Their mission is a major step in China’s plan 【小题6】(complete) the space station by December 2022, 【小题7】 it’s expected to be fully crewed and operational

Before then, China plans to send three more manned spacecraft and two laboratory modules to the space station.

It’s an 【小题8】 (ambition) target for China’s rapidly expanding space program, which has received 【小题9】(billion) of dollars in government investment and achieved a series of other milestones in recent years - including landing a lunar probe in a 【小题10】 (previous) unexplored area of the moon last December, and landing a rover on Mars in May.

The first creature to orbit our planet was just three years old, saved from the streets of Moscow only more than a week 【小题1】 her historic travel. Her name was Laika. Her 1957 flight paved the way for space exploration at the time 【小题2】 scientists didn’t know if a space flight was deadly for living creatures.

Man is a born explorer. Since before the dawn of civilization, we’ve been trying 【小题3】 （go）over the horizon to find food or more space, or just to see what’s beyond those trees or mountains or oceans. Our 【小题4】 （able）to explore has reached new heights in the last hundred years. Airplanes could 【小题5】 （simple）our travel, shorten distances and show us Earth from a new angle. By the middle of the last century, we aimed even 【小题6】 （high）.

Laika 【小题7】 （follow）into orbit three years later by the first human, Soviet cosmonaut Yuri Gagarin. It was our first step into space. Then we turned our sights to the moon and the solar system. Manned space stations began shining brightly in the sky.

Space travel is 【小题8】 like that in the movies .Getting from planet to planet（or moon）across the solar system requires complex calculations 【小题9】 （involve）inertia（惯性）and gravity-literally, rocket science. Space is also 【小题10】 （safe）. More than 20 astronauts have died, doing their job. However, that hasn’t stopped people from singing up and going into space.