以坡口形式看x坡口角变形比v形坡口的角变形（）。

局部通风机用于掘进工作面采用的是（）通风方法。

下列每个加工步骤的危害及其来源。

内包装

阅读理解。

     In many cultures white is often associated with something positive. A white-collar job, for instance,

is the kind of job many people look for, working with your brain and not your hands.

     White has a clean and pure image.That is why doctors, dentists, and nurses usually wear white

uniforms. Babies are dressed in white at baptisms (洗礼) and brides wear white wedding gowns at

weddings.White in these cases is the symbol of innocence or purity.

     Sometimes white is used in expressions that are not good. "Whitewash" is one such expression.At

first, "whitewash" meant to paint over something with white paint to make it look better. However, it

means something different today: to hide or to cover up mistakes or failures.

     A "white elephant" is another example of white used in a negative way. In ancient Thailand, a white

elephant was regarded as a sacred animal, but it was very expensive to keep. The kings of those days

presented a white elephant to the people they wanted to ruin.Once they received this holy, royal animal

      as a gift, they were not allowed to sell or kill it.Today, a "white elephant" means something that is

big, useless, and unwanted. In America, when people want to get rid of their furniture or clothes, they

often have a "white elephant sale".

1. The text is mainly about _____.

A. the meanings of white in English culture

B. the history of some English idioms

C. some interesting customs in English culture

D. some useful English words and expressions

2. Which expression has an historical background?

A. White-wash.

B. White-collar.

C. White elephant.

D. White elephant sale.

3. In which statement does"white" have a negative meaning?

A. A boy is dressed in white at baptisms.

B. A bride wears a white wedding gown.

C. A man whitewashes his crime.

D. A girl finds a white collar job.

4. The author develops the text mainly by ______.

A. analyzing its cause and effect

B. providing typical examples

C. comparing different ideas

D. following the time order

以下哪几种情形属于违规制造、销售枪支罪？（）

A.甲私自从网上购得大量的手枪部件，私自拼装手枪并销售

B.乙是国家认可的枪支制造企业，但是在制造枪支的过程中，因为技术问题，导致生产了一批重号的枪支

C.枪支销售企业丙一直在境内私下销售为出口而制造的枪支

D.枪支制造企业丁，经常超限额的生产规定枪支以为私下销售获利

下列哪种平面流动的等势线为一组平行的直线（）

A.汇流或源流

B.均匀直线流

C.环流

D.转角流