题目内容:
[A]Because it is full of challenges for human beings.[B]Because it may be necessary for human beings to survive.
[C]Because it is the greatest adventure in human history.
[D]Because it is more exciting than any other adventures.
参考答案:
[B]Because it may be necessary for human beings to survive.
[C]Because it is the greatest adventure in human history.
[D]Because it is more exciting than any other adventures.