背镗循环G87中，在孔底的动作为（）。A、朝着刀尖方向进给一个位移，主轴反转 B、朝着

Here are little cars that may some day take the place of today’s cars. If everyone drives such a car in the future, there will be less pollution in the air. There will also be more parking spaces in cities, and the streets will be less crowded. Three such Cars fit in the space now needed for one Car of the usual size. The little cars will cost much less to own and to drive. Driving will be safer, too, as these little cars can go only 55 miles per hour. The Cars of the future will be fine for getting around a city, but they will not be useful for long trips.

What’s about the cost of owning and driving such cars
The little cars will cost（）to own and to drive.

反映建筑材料与水性质有关的指标有( )。

A．吸水性与吸湿性

B．吸水率与含水率

C．软化系数

D．抗冻性与抗渗性

E．抗冻标号与渗透系数

氧分压在（）对机体细胞有毒性，氧中毒类型有（）、（）。

氢分压的工艺指标是≮（）MPA、

A、6.0

B、6.8

C、7.5

在Dreamweaver中，按（）组合键可以打开“CSS样式”面板。