问题 单项选择题

儿童期长骨发育和X线解剖表述错误的是()

A.儿童长骨为软骨内化骨

B.出生时骨干未完全骨化

C.骺软骨尚未完全骨化

D.儿童长骨由骨干、干骺端、骨骺板及骨骺组成

E.出生时股骨下端、胫骨上端即可见二次骨化中心

答案

参考答案:B

解析:儿童长骨来自软骨内化骨,有3个以上骨化中心,1个在骨干,另外的在两端(骨骺)。前者称为原始骨化中心或一次骨化中心,最早可在胚胎第6周出现;后者为继发骨化中心或二次骨化中心。出生时骨干已完全骨化,而两端仍为软骨,称骺软骨。出生后,两端骺软骨内出现继发骨化中心,但股骨下端、胫骨上端及肱骨上端骨骺于出生时即可见二次骨化中心。儿童长骨的主要特点是骺软骨,且未完全骨化,儿童长骨由骨干、干骺端、骨骺板及骨骺组成。

阅读理解

阅读理解

     Even plants can run a fever, especially when they're under attack by insects or disease. But unlike

human, plants can have their temperature taken from 3,000 feet away-straight up. A decade ago,

adopting the infrared(红外线)scanning technology developed for military purposes and other satellites,

physicist Stephen  Paley came up with a quick way to take the temperature of crops to determine which

ones are under stress. The goal was to let farmers precisely target pesticide(杀虫剂)spraying rather than

rain poison on a whole field, which invariably includes plants that don't have pest problems.

     Even better, Paley's Remote Scanning Services Company could detect crop problems before they

became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured

the heat emitted by crops. The data were transformed into a colourcoded map showing where plants

were running "fevers". Farmers could then spotspray, using 50 to 70 percent less pesticide than they

otherwise would.

      The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted

the new technology and longterm backers were hard to find. But with the renewed concern about

pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation.

Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of

agricultural land in the United States, " says George Oerther of Texas A & M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade.   But only if Paley finds the financial backing which he failed to obtain 10 years ago.

1. Plants will send out an increased amount of heat when they are________.

A. facing an infrared scanner

B. sprayed with pesticides

C. in poor physical condition

D. exposed to excessive sun rays

2. In order to apply pesticide spraying precisely, we can use infrared scanning to________.

A. estimate the damage to the crops

B. draw a colourcoded map

C. measure the size of the affected area

D. locate the problem area

3. Farmers can save a considerable amount of pesticide by________.

A. resorting to spotspraying

B. transforming poisoned rain

C. consulting infrared scanning experts

D. detecting crop problems at an early stage

4. The application of infrared scanning technology to agriculture met with some difficulties-________.

A. its high cost

B. the lack of official support

C. the lack of financial support

D. its failure to help increase production

单项选择题