金属桥用栅栏式的铸道其优点（）。 A.各个铸道的长度一致，有利于防止收缩变形 B.各

氢火焰离子化检测器通常使用的氮气-氢气-空气的流量比是（）

A.3：30：300

B.30：30：30

C.30：30：100

D.30：10：300

E.30：30：300

Part 1V  Writing (45 marks)Section A (10 marks)

Directions: Read the following passage. Fill in the numbered blanks by using the

information from the passage.

Write NO MORE THAN THREE WORDS for each answer.

An apprenticeship is a form of on-the-job training that combines workplace experience and classroom learning. It can last anywhere from one to six years, but four years is typical for most. An apprentice spends the majority of the time in a workplace environment learning the practical skills of a career from a journeyman--someone who has done the job for many years. The rest of the apprentice's time is spent in a classroom environment learning the theoretical skills the career requires. Being an apprentice is a full-time undertaking.

One of the advantages of apprenticeship is that it does not cost apprentices anything. The companies that hire them pay for school. What's more, it offers apprentices an "earn while you learn" opportunity. They usually start out at half the pay of a journeyman, and the pay increases gradually as they move further along in the job and studies. Near the end of the apprenticeship, their wages are usually 90 percent of what a journeyman would receive. Apprenticeship also pays off for employers. It can offer employers a pool of well-trained workers to draw from.

Despite the advantages, apprentices are usually required to work during the day and attend classes at night, which leaves little time for anything else. Sometimes, they might be laid off(下岗) if business for the employers is slow.

Once they have completed the apprenticeship and become journeymen, they receive a nationally recognized and portable certification and their pay also increases again. Some journeymen continue employment with the companies they apprenticed with; others go onto different companies or become self-employed contractors.

识别混响伪像的方法有（）.

A.适当侧动探头，使声束垂直于胸壁或腹壁

B.适当侧动探头，使声束勿垂直于胸壁或腹壁

C.加压探测见多次反射的间距缩小

D.减压探测可见多次反射间距加大

E.降低仪器增益可使伪像消失

(由单选和多选组成。)
（一）资料

根据美国一些经济学家的统计，在美国，上大学的间接成本大约占到上大学的全部成本的( )。

A．10%～20%

B．30%～40%

C．40%～50%

D．60%～70%

当渠道流量一定时，渠底比降大，则（）

A.引起渠道淤积

B.控制面积变大

C.过水断面面积小

D.工程量大