企业级数据仓库的数据模型通常包括（）。
A.实体关系模型
B.预估模型
C.多维模型
D.分类模型
参考答案：A, C
He ___________busy yesterday, or he __________you with your experiment.
A．was; had helped
B．was; would have helped
C．had been; would have helped
D．were; would have helped
基准物只要其组成与化学式相符就可以。（）
