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叙述说明FRANCOTOSI燃煤锅炉板式过热器管子外径、节距、受热面积及材质。

答案

参考答案：

管子外径为50.8mm，横向节距为2743.2mm（中心部位为3429mm，端部为2514.6mm），纵向节距为60.5mm，受热面积为636m2，材质为A213－T11、A213－T22和A213－TP347H。

单项选择题

It is clear that some chemicals can damage the health of animals and humans. (1) , this is not the only problem that (2) be caused by the careless use of chemicals. Chemicals can also (3) the ecological balance of the environment. If the ecological balance is disturbed, the results can be (4) serious.The (5) of DDT illustrates the problem. DDT, a chemical which kills insects, at first seemed to be a perfect answer (6) many problems. It would control insects that caused dangerous diseases, (7) insects that caused billions of dollars of damage to crops every year. Governments permitted and even (8) the use of DDT. Farmers in many countries (9) to spray it on their crops. The (10) results were good. Damage to crops (11) down, and profits went up. However, the chemical had effects which the scientists didn’t see in (12) . First, it also killed insects which were the (13) enemies of the harmful insects and which were therefore beneficial to farmers. Second, and perhaps worse, DDT did not kill (14) harmful insect. A few insects had natural resistance to the chemical. They (15) and reproduced in large numbers. In a few years there were large numbers of insects which were not (16) by DDT, and there were (17) insects which Could act as natural (18) on these new "super-insects". Finally, it became clear that DDT was not solving the insect problem. In fact, it was making the problem worse. It (19) became necessary to find a second (20) for the effects of the first.

第（2）空应选择（）

A．can

B．must

C．will

D．shall
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填空题

CDMA2000 1x系统反向功率控制分为（）和（）两种。
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