顺流航行时的实际航速比顶流航行时的实际航速（）。
A.大二倍的流速
B.大三倍的流速
C.大四倍的流速
参考答案：A
Professor Hunter was soon told ____he discovered was not important to them.
A．why that
B．why what
C．that why
D．what why
组成坐骨神经的神经根纤维为（）
A.L1～L2
B.L4～L5
C.L1～S2
D.L4～S3
E.S1～S5
