在Word中，若要隐藏绘图工具栏，应选择（）命令。 A."视图"下拉菜单中的"工具栏

圆锥型套筒冠义齿基牙制备正确的是()

A．各轴壁的预备量比一般金属烤瓷全冠基牙预备量大

B．牙周组织有破坏吸收的磨牙面可预备出2.5mm，甚至大于2.5mm的间隙

C．各轴面的牙体颈缘应制备出宽度为0.8～1.0mm的肩台

D．颈缘可制成直角肩台或斜面肩台

E．牙体各轴壁的轴角应圆钝

可见于运动员的是（）

A.窦性心动过速

B.窦性心动过缓

C.心房颤动

D.预激综合征

E.病态窦房结综合征

NASA has opened the door to the next generation of space discovery by announcing great plans for a base for humans to live on the surface of the moon forever.

The project to build a base on the moon will begin soon after 2020, with astronauts living there within four years.

The project comes after several excellent scientists and environmentalists asked humans to look beyond Earth to ensure the survival of the species (物种).

Eventually, the moon will be a base for humans to explore the solar system and one day land on Mars.

NASA began planning for the first moon landing since 1972 when George Bush, the US president, announced his new plan for space exploration four years ago.

NASA has already talked about the design of the Orion spacecraft that will replace the old space shuttle fleet in 2010.

The plan for the moon base, however, is the first detailed explanation of how NASA intends to prepare for the first manned exploration of deep space and a possible Mars mission within 30 years.

Scientists also believe that the south pole on the moon contain rich natural gases such as the rare helium-3 that could be used as fuel for the generation of nuclear power. Besides, teams of astronauts living there for six months at a time would mine for hydrogen and oxygen to make water and possibly rocket fuel.

小题1:When was the plan to explore space first announced according to the passage?

A．In 1972.

B．In 1950.

C．In 1968.

D．In 2020.小题2:The reasons why NASA has begun the plan to explore space include the followings except ________.

A．to protect Earth

B．to explore deep space

C．to finish Mars mission

D．to show how powerful the USA is小题3:In the future, when people fly to the moon, they will probably not bring with them too much ________

A．hydrogen

B．food

C．oxygen

D．water小题4:The passage mainly talks about ________.

A．the USA’s new plan for space exploration

B．how to build a base on the moon

C．why to ensure the survival of the species

D．where to get new natural resources

怎样判断直流发电机不充电的原因？

民用建筑工程室内装修中哪些材料必须有游离甲醛含量或游离甲醛释放量的检测报告？