渡口经营者应当在渡口设置明显的标志,维护渡运秩序,保障渡运安全。
参考答案:对
If Newton lived today,he would be surprised by what_____in science and technology.
A.had discovered
B.had been discovered
C.has discovered
D.has been discovered
什么是瘢痕体质?为什么瘢痕体质的患者不能做手术?