题目内容：

阅读下面材料，在空白处填入1个适当单词或括号内单词的正确形式。

The Moon’s near side，the one we all see，has been the target of many robotic and human missions.However，its far side，also 1. (call)the dark side because it faces away from the Earth and little 2. (know)about it，has never been explored.That changed on Jan.2，2019，when Chinese spacecraft Chang’e 4 made a soft landing on 3. is often referred to as the dark side.

The landing is 4. example of China’s growing desire 5. (compete)with the American，Russian and European space programs.China also wants to 6. (strength)its position as a regional and international power.

One of the great 7. (difficulty)in exploring the far side of the Moon is that it blocks all radio signals，8. (make)it impossible to communicate with the Earth.To overcome this difficulty，in 2017，the Chinese National Space Administration launched a satellite to orbit the Moon and relay the signals.Once a 9. (rely)communication path was in place，Chang’e 4 could send back information.

Chang’e 4 will make astronomical observations and examine the structure and mineral composition of the ground above and below the surface，10. researchers believe will provide insights into the solar system’s early days and perhaps even the origin of the first stars.