题目内容：

最近，你班同学就“太空探索是否值得”这一话题展开了一场讨论。请你根据下表提供的信息，用英语写一篇短文介绍讨论的情况。

注意：

1. 词数：120左右；

2. 参考词汇：短缺 shortage (n.); 太空探索space exploration

3. 文章开头和结尾已给出

Dear David,

I’m glad to receive your letter asking me about our discussion on whether space is worth exploring. Now I’m writing to tell you our opinions.

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