Chinese astronauts in Tiangong space station opened a science lecture on December 9th, 2021 as they traveled around     1     Earth.

There     2     （be）a lecture and some interesting activities on that exciting day. First, Zhai Zhigang, Wang Yaping and Ye Guangfu, all members of the Shenzhou XIII mission crew, greeted students, teachers and other participants as the lecture began at 3:40 pm. They then showed viewers the place     3     they live and work. The astronauts carried out experiments     4     （show）interesting physical phenomena（现象）in space,     5     （include） "disappearing buoyancy（浮力）" and a "water ball". At last, before the end of the livestreamed activities, they     6     （happy）answered questions from students.     7     （million）of primary and middle school students across China watched the 60-minute televised event, which was the first lecture of the Tiangong Class, China' s first extraterrestrial（地球大气圈外的）lecture series to make students interested     8     space science.

The manned space agency said that more lectures would     9     （hold）based on the country's manned spaceflights and would also be presented by some     10     （profession）Chinese astronauts. Such activities are intended to spread knowledge about manned spaceflights for science among young people.