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问题 单项选择题

对于C++流运算符＞＞，说法正确的是 ______ 。

A．它可以重载为类的友元或成员函数

B．它是流类的一个输出运算符

C．C++内预定义了各种基本数据类型的输入操作

D．可以直接用它输入类类型数据

答案

参考答案：C

单项选择题

A volcanic eruption in Iceland has sent ash across northern Europe. Airlines have stopped or changed the flights across the Atlantic Ocean, leaving hundreds of passengers stuck in airports.
Grimsvotn is one of the largest active volcanoes in Europe. What makes Grimsvotn different is that it lies under a huge glacier(冰川) of ice up to 12 meters thick. The hot volcano heats up the ice above it, which then forms a layer(M) of water between the glacier and the volcano. This layer of water puts pressure on the volcano ,keeping it stable. As the water flows out from under the glacier, the pressure Rifts. The lava(岩浆) from the volcano then comes up to the surface. This is exactly what has happened today.
Now, airlines have to make changes to their flights so as not to fly through the clouds of volcanic ash. According to KLM, one of Europe’s biggest airlines, airplanes cannot go under the cloud or over it. Going through the cloud can result in ash getting stuck in the airplane’s engines, causing damage to the plane.
The eruption has also caused problems for animals in Iceland. The volcano left ash and sharp, glass-like rocks all over the countryside. Farmers are keeping their animals inside to stop them from eating ash-covered grass or the sharp objects.

What makes Grimsvotn different from other volcanoes

A．It is below ice.

B．It lies under the sea.

C．It is the largest volcano.

D．Its lava affects the airlines.
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单项选择题

图示排架，已知各单柱柱顶有单位水平力时，产生柱顶水平位移为，D为与柱刚度有关的给定常数，则此结构柱顶水平位移为：（）

A.A

B.B

C.C

D.D
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