第1空 19. A ) Space exploration has serious consequences . B ) India has many space exploration programs . C ) There is quite a lot to learn about the moon . D ) A lot of garbage has been left on the moon . 第2空 20. A ) It is costly to bring back . B ) It is risky to destroy . C ) It is of no use on Earth . D ) It is damaged by radiation . 第3空 21. A ) Record details of space exploration . B ) Monitor the change of lunar weather . C ) Study the effect of radiation and vacuum on its materials . D ) Explore the possibility of human settlement on the moon .