两个大小相等的力产生的效果一定相同。[ ]

若函数y=（m+2）x²+2x-3的图象是抛物线，则m的值为______，该抛物线的开口方向______．

A survey of the opinions of experts ____ that three hours of outdoor exercise a week ____ good

for one's health.      [ ]

A. show; are                

B. shows; is      

C. show; is                      

D. shows; are

The order came that the medical supplies ______ to the village without delay.

A．would be sent

B．should send

C．be sent

D．must be sent

Windows 98的注册表中存储了系统的所有配置数据，用户可以通过“注册表编辑器”查看或编辑注册表中的信息。如果要启动“注册表编辑器”，用户必须在“运行”对话框中输入并执行命令______。

住宅照明分支网路为截面不应小于( )mm²的低压绝缘铜芯线。

A．2.5

B．4

C．6

D．10