直接暴力所致的骨折常为：
A．裂纹骨折
B．嵌插骨折
C．压缩骨折
D．横断骨折
E．斜形骨折
参考答案：D
旅游文化未来的发展有哪些趋势？
It is difficult for us to learn a lesson in life ______ we've actually had that lesson.[ ]
A. when
B. after
C. since
D. until
