下列河流中，冬季不结冰的是（ ） A．黑龙江 B．辽河 C．黄河 D．长江

Our sense of smell, which we normally take for granted, is nowadays being increasingly used for purposes which might surprise us if we realized them.

One area in which smells are created to achieve particular results is marketing. For some time producers have taken advantage of our sense of smell with regard to household goods.

When pleasant smells are passed through a store’s air conditioning system, people tend to spend more time in the store and buy more. For example, the smell of chocolate is used in sweet stores, while the smell of leather and perfume are used in clothes stores.

In a test, people looked at the same types of shoes in two rooms—one filled with purified air, the other with a smell of mixed flowers. Eighty-four percent of the people preferred the shoes in the room with the smell of flowers. In fact, many said they would have paid up to US $ 10 more for a pair.

Smells also have other uses. Research has shown that certain smells can help to calm anxious people and increase their feeling of safety. Smells such as that of flowers and pine forests might therefore be used to relax patients in doctors’ and dentists’ waiting rooms, and to make the environment more pleasant and less stressful to them.

Some companies are experimenting with different smells to produce different efferent effects on their workers according to the time of day.

For example, early in the morning they might put the smell of lemon in the air conditioning system to wake people up. In the middle of the morning, when the atmosphere tends to become more tense, the smell of wood could be used to calm people down. Before lunchtime the smell of melting butter would encourage people to go to lunch on time. After lunch, when people often begin to lose attention, the smell of mint would increase their watchfulness.

While some of these uses of smells may e helpful and effective, not everyone would agree with their use to control customers in stores. It has been suggested by consumers’ organizations that one way to avoid this new subconscious（无意识）pressure to buy is to go shopping when people are less likely to be influenced by smells.

小题1:We can conclude from the text that      

A．smells are widely used in different shops

B．different smells can keep people feel happy

C．smells are effective if used in suitable cases

D．hospitals take advantages of the sense of smell小题2:What kind of smell is effective when the students are having a lesson according to the text?   Butter.        B. Leather        C. Wood        D. Mint

小题3:The 4th paragraph proves that       

A．pleasant smells attract people’s attention to stores

B．people prefer the shoes with the smell of different flowers

C．right smells increase people’s view of the value of a product

D．people want to pay more money because of good smells小题4:What does the underlined word “them” in paragraph 5 refer to?

A．patients

B．doctors

C．smells

D．waiting rooms

下列因素中：

（1）温度；

（2）压力；

（3）惰性气体的含量；

（4）容器的大小；

（5）火源的性质。

影响煤气爆炸极限正确的是：（）

A、全对；

B、有三个对；

C、有二个对；

D、有四个对。

常用的风动凿岩机和局部通风机都是风动工具。

实施RBI的压力容器，确定其检验周期以压力容器的剩余使用年限为依据，检验周期最长不超过压力容器剩余使用年限的一半，并且不得超过（）年。

A、3

B、7

C、9

我国生产的抽油杆从级别上分有（）、（）、（）三种级别。