在销的装配中,被联两件为平面结合时,上、下销孔多是()。
A、上松下紧
B、上紧下松
C、上下一致
参考答案:A
Mother bought me 3 books on English study, the second ________ I really liked.
A.of that
B.of which
C.that
D.which
计算机的存储系统一般指主存储器和辅助存储器。