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问题 单项选择题 A3/A4型题

在诊断放射学中，被照体对X线的吸收主要是光电吸收。特别是使用低kV时，光电吸收随物质原子序数的增加而增加。人体骨骼由含高原子序数的钙、磷等元素组成，所以骨骼比肌肉、脂肪能吸收更多的X线，它们之间也就能有更高的对比度。组织密度愈大，X线吸收愈多。人体除骨骼外，其他组织密度大致相同。肺就其构成组织的密度来讲与其他脏器相似，但活体肺是个充气组织，空气对X线几乎没有吸收，因此肺具有很好的对比度。人体各组织对X线的衰减，由大变小的顺序是（）

A.骨、脂肪、肌肉、空气

B.骨、肌肉、脂肪、空气

C.脂肪、骨、肌肉、空气

D.肌肉、骨、脂肪、空气

E.肌肉、脂肪、骨、空气

答案

参考答案：B

单项选择题

阅读下面短文，从短文后各题所给的四个选项（A、B、C 和 D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

                                    A Heroic Driver

Larry works with Transport Drivers. Inc. One morning in 2009. Larry was  41

along 165 north after delivering to one of his    42   . suddenly, he saw a car with its bright lights on.    43    he got closer, he found 44    vehicle upside down on the road. One more look and he noticed    45    shooting out from under the    46    vehicle. Larry pulled over, set the brake and    47   the fire extinguisher (灭火器). Two good bursts from the extinguisher and the fire was put out.

The man who had his bright lights on    48    and told Larry he had    49    an emergency call. They    50    heard a woman’s voice coming from the wrecked (毁坏的) vehicle.    51   the vehicle, they saw that a woman was trying to get out of the broken window. They told her to stay    52    until the emergency personnel arrived,    53    she thought the car was going to    54   . Larry told her that he had already put out the fire and she should not move    55    she injured her neck.

Once fire and emergency people arrive, Larry and the other man    56    and let them go to work. Then, Larry asked the    57    if he was needed or    58    to go. They let him and the other man go.

One thing is    59   —Larry went above and beyond the call of duty by getting so close to the burning vehicle! His    60    most likely saved the woman’s life.

59（）

A.for certain

B.for consideration

C.reported

D.checked
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名词解释

Boyce-Codd范式（BCNF）
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