10以内加减教学的安排通常是()
A.学习解答口述应用题
B.理解加减含义
C.利用数的组成学习加减
D.巩固对加减的认识
参考答案:A, B, C, D
With a lot of problems ___________,the newly-elected president is having a hard time.[ ]
A. settled
B. settling
C. to settle
D. to be settled
在关系模型中,若属性A是关系R的主码,则在R的任何元组中,属性A的取值都不允许为空,这种约束称为______规则。