单选题：had easily established itself as the fastest method of trave

题目分类：中级
题目类型：单选题
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题目内容：

had easily established itself as the fastest method of traveling great distances. A．Sea travel
B．Land travel
C．Air travel

参考答案：

答案解析：

At one time,________were the only practical way to cross the

At one time,________were the only practical way to cross the vast areas of the w

分类：中级题型：单选题

6._________

6._________

分类：中级题型：单选题

2._________

2._________

分类：中级题型：单选题

回答第11题。

回答第11题。

分类：中级题型：单选题

21__________

21__________A．accident B．conspiracy C．hope D．dream

分类：中级题型：单选题