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问题 单项选择题 A型题

关于二尖瓣狭窄的超声心动图征象的描述，不正确的是（）。

A.胸骨旁二尖瓣水平左室短轴位显示二尖瓣前后叶增厚，瓣口面积缩小

B.M型超声心动图二尖瓣前叶舒张期充盈速度明显减慢，呈城墙样改变

C.左心室内径增大

D.合并心房颤动时，左心房或左心耳内可出现血栓

E.重度二尖瓣狭窄或晚期可出现肺动脉高压

答案

参考答案：C

解析：单纯二尖瓣狭窄时，一般左心室内径正常，左心房增大。

选择题

下列有关生产、环保、资源问题叙述错误的是[ ]

A．长期使用硫酸铵会使土壤呈酸性，应将硫酸铵与熟石灰混合使用

B．“温室效应”主要是由二氧化碳等气体引起的

C．pH＜5.6的酸性降水称为酸雨，它的形成与大气中SO2等酸性污染物增多有关

D．煤和石油是不可再生资源，必须综合利用以提高利用率
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单项选择题

Questions from 31 to 35 are based on the following passage: Generally, cargo is carried in containers, but sometimes it is still shipped as breakbulk cargo. During the voyage, goods may be stacked on top of or come into violent contact with other goods. And the cargo might be dragged, pushed, rolled, or dropped during unloading, while moving through customs, or in transit to the final destination. Moisture is a constant concern because condensation may develop in the hold of a ship even if it is equipped with air conditioning and a dehumidifier(除湿机). Another aspect of this problem is that cargo may also be unloaded in precipitation, or the foreign port may not have covered storage facilities. Buyers are often familiar with the port systems overseas, so they will often specify packaging requirements. If the buyer does not specify this, be sure the goods are prepared using these guidelines: Pack in p containers, adequately sealed and filled when possible. To provide proper bracing in the container, regardless of size, make sure the weight is evenly distributed. Goods should be palletized when possible containerized. Packages and packing filler should be made of moisture-resistant material. To avoid pilferage, avoid writing contents or brand names on packages. Other safeguards include using straps, seals, and shrink wrapping. Observe any product-specific hazardous materials packing requirements. Normally, air shipments require less heavy packing than ocean shipments, though they should still be adequately protected, especially if they are highly pilferable. Finally, because transportation costs are determined by volume and weight, specially reinforced and lightweight packing materials have been developed for exporting. Packing goods to minimize volume and weight while reinforcing them may save money, as well as ensure that the goods are properly packed.

The packing of cargo delivered by air freight can be（）

A．slighter than that of the freight carried by sea

B．heavier than that of the freight carried by sea

C．more pilferable

D．more protective
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