连接运算是将两个或两个以上的关系根据连接条件生成一个 【1】 。

短文填空。

    根据短文内容和首字母提示，把所缺单词填写在短文后面相应的横线上，使句意完整。

    When you laugh, you will o  1   your mouth and show your teeth. The healthier those teeth are, the happier you look. Why is that?

    It’s because your teeth are important in many w  2   . If you take care of them, they’ll help to take care of you. Strong healthy t  3   help you eat the right food to help you grow. They also help you speak clearly.

    Brush your teeth t  4    a day-after breakfast and before bedtime.

    You also need to care about w  5   you eat and drink. Eat lots of fruits and vegetables and drink water instead drinks.

1.___________  2.___________  3.___________  4.___________  5.___________

救唇汤功效与作用

工程建设项目职业健康安全与环境管理的特点不包括（）。

A．经济性

B．复杂性

C．间歇性

D．协调性

E．单一性

简述烤烟大田期需水规律及灌溉技术。

举出6种以上金属件常用的表面处理方法。