单项选择题Directions:Please choose the best answer from the following 4 choices, and fill in the blanks with the corresponding letter. We were early for our appointment, so we _____ at a bookstore. A、race against time B、time has come C、time out D、kill time
单项选择题人首先必须活着,然后才能做别的事情。
单项选择题转向器是转向系统中减速增扭的传动装置。 A、正确 B、错误
不定项选择高尔基复合体的发生来源于内质网和核膜
单项选择题土石坝地基处理中,( )结构简单、工作可靠、防渗效果好,得到了广泛的应用。缺点是其施工和坝体填筑不便同时进行,若汛前要达到一定 的坝高拦洪渡汛,工期较紧。 A. 混凝土防渗墙 B. 粘土截水墙 C. 钢板桩 D. 帷幕灌浆