There ______ many bikes in the streets ten years ago. [ ]
A. was
B. is
C. are
D. were
答案:D
“阿拉伯数字”产生于[ ]
A.尼罗河流域
B.两河流域
C.印度河流域
D.黄河流域
中断系统包括 【1】 和中断处理程序。