图纸上尺寸标注默认的倒角度数是（）倒角。
A、30°
B、45°
C、60°
D、90°
参考答案：B
Our hometown is quite different from _______before.
A．that is was
B．what it was
C．which it was
D．when it was
将E-R图转换到关系模式时，实体与联系都可以表示成
A) 属性 B) 关系 C) 键 D) 域
