依据ISO15189,所有与质量管理体系有关的文件均应能惟一识别,必须包括()
A.标题
B.版本
C.页数
D.授权发行
E.来源识别
参考答案:A, B, D, E
解方程:(x-2)(x-3)=9-x2
-Excuse me, does Mr Smith’s son live here?
-He _________ be here, but he has moved.
A.has to
B.used to
C.tried to
D.happened to