对急性脑梗死患者，下列哪种情况不适于溶栓治疗（） A.发病6小时以内 B.CT证实无

专为升降物料的井筒，其最高允许风速为（）。

与上山法施工相比，下山法施工要解决的主要问题是（）。

A.控制巷道的方向和倾角

B.通风和防止瓦斯积聚

C.设备防滑和预防跑车事故

D.避免工作面积水

A growing number of students in the United States are studying Mandarin(普通话). It is the official language of China. More and more people speak Mandarin than those who speak other languages in the world.

Schools that teach Mandarin want to prepare students for a future in which they are likely to work with people from China. Business in China is booming(繁荣的), and that trend(趋势) is expected to grow.

The US government is trying to encourage even more public schools to teach Mandarin. Officials are considering spending about $1 billion on Mandarin programs in schools. China is getting involved(参与) too. The Chinese government has donated Mandarin textbooks to US schools. Some schools are also taking part in teacher exchange programs with China.

“It is important for students to learn Mandarin and Chinese culture,” said Mary Patterson, a school principal(校长) in Portland, Oregon. “Students who do so will have wider opportunities when they become adults.”

小题1:Why are US schools teaching Mandarin?

A．To help students communicate with Chinese students.

B．To encourage students to move to China,

C．To prepare students for the future.

D．To get students interested in business.小题2:The underlined word “donated” (in Paragraph 4) can be replaced by “______”?

A．provided

B．kept

C．made

D．found小题3: What is the best title for this passage?

A．Why US students learn Mandarin

B．Schools in China

C．How to speak Mandarin

D．China today

石油焦执行的质量标准是什么？

三相负载作Y连接时，只要有了中性线，就不会发生中点位移的现象。（）