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问题 单项选择题

下列哪个选项是合法的标识符

A．类用于描述事物的属性和对事物的操作

B．类与类之间通过封装而具有明确的独立性

C．类与类之间必须是平等的关系，而不能组成层次结构

D．类与类之间可以通过一些方法进行通信和联络

答案

参考答案：C

解析：与AWT不同的是，Swing构件不能直接添加到顶级容器中，它必须添加到一个与Swing贝级容器相关联的内容面板。内容面板是顶级容器包含的一个普通容器，它是一个轻量级构件。

多项选择题

关于干气水洗罐（D-101）压力波动的原因，下列说法正确的是（）。

A.罐顶压控故障

B.排出管路不畅通

C.干气进料不稳定

D.水洗循环流量低
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单项选择题

"What does the middleman do but add to the price of goods in the shops " Such remarks are aimed at the intermediate operations between manufacturers and final customers. This practice usually attracts a lot of attention from the public and the press and the operation most talked about is what is often called wholesaling.The wholesaler buys goods in large quantities from the manufacturers and sells them in smaller parcels to retailers, and for this service his selling price to the retailer is raised several percent higher. But his job is made more difficult by retail demand not necessarily running level with manufacturers’’ production. Because he adjusts or regulates the flow of goods by holding stock until required, he frees the manufacturer, to some extent, from the effect on production of changing demand and having to bear the whole risk.The manufacturer can then keep up a steady production flow, and the retailer has no need to hold heavy stocks, who can call on the wholesaler for supplies any time. This wholesale function is like that of a valve in a water pipe. The middleman also bears part of the risk that would otherwise fall on the manufacturer and also the retailer.The wholesaler provides a purely commercial service, for which he is too well rewarded. But the point that is missed by many people is that the wholesaler is not just someone adding to the cost of goods. It is true one could eliminate the wholesaler but one would still be left with his function: that of making sure that goods find their way to the people who want them.

A middleman’s work may become difficult because________.

A．manufacturers run their production on a much higher level

B．market demand may not be the same as industrial production

C．retailers are not necessary in running their retailing business

D．retailers demand lower levels than those demanded by manufacturers
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