平面直角坐标指示目标和确定点的位置时，应按什么顺序进行？（）A、先横坐标后纵坐标 B

三角形的三边长分别为8，15，17，这个三角形的面积是[ ]

A．60

B．120

C．68

D．136

从5时到8时30分经过了[ ]

A．4小时30分

B．2小时30分

C．3小时30分

句型转换

1. Daming is going to play football with his friends this afternoon.  ( 对画线部分提问 )                                               

                     Daming                             with his friends this afternoon?

2. He's going to meet John in the park.  (改为否定句)    

He                             meet John in the park.

3. I am going to go shopping. (改为同义句)    

I am going to                            .

4. There is a school meeting on the playground. ( 用 this afternoon改写）  

There is                                 a school meeting on the playgrouncl this afternoon.

5. He is going to play computer games this evening.（改为一般疑问句） 

        he                             computer games this evening?

在选择零件的表面粗糙度时，其Ra值应（）。

A.愈小愈好；

B.愈大愈好；

C.为定值；

D.在满足零件的性能和工作要求的前提下，选用较大的Ra值。