增加铁水中含碳量对其铸铁性能的影响是（）。 A.机械强度提高 B.机械强度降低 C.

Today I took part in the English singing competition of our school. Most of the singers and audience have been there when I arrived at the ball. See the large audience, I started to feel little nervous. After some times, it was my turn to sing. When the host read my name out, the audience burst into a great cheer, and my heart began to beat really fastly. The song I sing was Country Road, that is a very famous piece of American country music. I had practiced for it many times, and I didn’t think I had done a very good job. Anyway, I was still very excited because of participating was the most important thing to me.

索赔按目的划分包括( )。

A．综合索赔

B．单项索赔

C．工期索赔

D．合同内索赔

E．费用索赔

有关类和对象的说法不正确的是( )。

A．对象是类的一个实例

B．任何一个对象只能属于一个具体的类

C．一个类只能有一个对象

D．类与对象的关系和数据类型和变量的关系相似

公共支出的原则不包括( )。

A．经济效益原则

B．公平原则

C．统筹兼顾原则

D．诚实信用原则

用检偏器观察某束光，如果环绕光的传播方向转动检偏器，透射光强也随之变化，则该某束光为( )。

A．非偏振光
B．圆偏振光
C．面偏振光
D．椭圆偏振光