椎基底动脉系统短暂性脑缺血发作最常见的症状是（）。
A.眩晕
B.耳鸣和耳聋
C.跌倒发作
D.吞咽困难
E.复视
参考答案：A
— How amazing it is that astronauts are exploring outer space!
— It's a challenge, I guess, _____ man against nature. [ ]
A. of
B. for
C. by
D. about
安全性是指货物在到达目的地的状态与开始托运的状态相同。 ( )
