边坡工程按《岩土工程勘察规范》(GB50021-2001)(2009版)勘察时,可不包括下列()阶段()
A.可行性研究勘察
B.初步勘察
C.详细勘察
D.施工勘察
参考答案:A
等边三角形的边长为4,则此三角形外接圆的半径为 。
He spent as much time as he could ______ his spoken English. [ ]
A. improve
B. improving
C. to improve
D. improved