A. She went cycling in the nature park.
B. Three years ago.
C. Yes, there were.
D. No, there wasn't.
E. There was a small house many years ago.
北京人制造和使用的劳动工具是( )
①弓箭 ②陶器 ③打制石器 ④磨制石器
下列说法中正确的是( )
图为某区域地质剖面示意图。导致图中甲处岩层顶部缺失的原因是( )