单项选择题
He's working hard for fear that he（）
A. should fall behind B. fell behind C. may fall behind D. would fall behind
单项选择题 In architecture (建筑学), a vault (拱顶) is a proof or ceiling in the （） of an arch.
单项选择题 Since you need to catch an early train tomorrow morning, we（）now.
单项选择题 Are the terms "pure" and "applied" two totally different activities, having little or no interconnection, as （）often implied
