Chinese astronauts conducted a science lecture 400 kilometers above Earth to millions of students on Thursday afternoon,as they orbited in the Tiangong space station.

Major General Zhai Zhigang,Senior Colonel Wang Yaping and Senior Colonel Ye Guangfu,all members of the Shenzhou XIII mission crew,greeted students,teachers and other ____9____(participate)when the lecture started at 3:54 pm.They showed viewers ____10____ they live and work inside the space station.

The astronauts displayed their exercise equipment and a specially ____11____(design)space suit,and ____12____(conduct)demonstrations on physical phenomena in microgravity,such as“disappearing buoyancy(浮力)”and a“water ball”.Ye Guangfu,____13____ is on his first spaceflight,showed how he rotated his body in the ____14____(weight)environment.The astronauts also answered questions from students during the lecture.

Tens of millions of primary and middle school students across China watched the hourlong televised event.It was ____15____ first lecture of the Tiangong Class,or Heavenly Palace Class,China’s first extraterrestrial(外星)lecture series to popularize space science.

More lectures ____16____(hold)based on the country’s manned spaceflights and will also be presented by Chinese astronauts,the manned space agency said.Such ____17____(activity)are intended to spread knowledge about manned spaceflights and spark enthusiasm ____18____ science among young people,it added.