问题 单项选择题

同时具备耐腐蚀、耐温及耐冲击的塑料水管是( ).

A.聚乙烯管

B.聚丙烯管

C.ABS管

D.聚氯乙烯管

答案

参考答案:C

解析:

聚乙烯塑料管:无毒,可用于输送生活用水,水管主要用聚氯乙烯管。聚丙烯管(pp管)系聚丙烯树脂经挤出成型而得,用于流体输送。按压力分为Ⅰ、Ⅱ、Ⅲ型,其常温下的工作压力为:Ⅰ型为0.4MPa、Ⅱ型为0.6MPa、Ⅲ型为0.8MPa。而ABS工程塑料管有耐腐蚀、耐温及耐冲击性能,均优于聚氯乙烯管,聚乙烯管,聚丙烯管。它由热塑性丙烯腈-丁二烯-苯乙烯三元共聚体黏料经注射、挤压成型加工制成,使用温度为ー20-70°C,压力等级分为B、C、D3级。所以正确选项为C。

考点:机电工程材料.

完形填空
完形填空。

      There are many different ways of seeing a town for the first time. One of them is to walk around it,
guide-book in hand. Of course, we may    1    with our guide-books the history and special developments
of a town and get to know them.    2    then, if we take our time and stay in a town for a while, we may
get to know it better. When we look at it as a whole, we begin to have some    3   , which even the best
guide-books do not answer. Why is the town just    4   this, this shape, this plan, this size? Why do its
streets    5   in this particular way, and not in any other way?
      Here even the best guide-book fails us. One can't find in it the information about how a town has
developed to the    6   appearance. It may not describe the original (最初的) design of a town. However,
one may get some ideas of what it    7   to look like by walking around the town. One can also imagine 
   8    the town was first planned and built. Then one can learn more about in what direction the town    9   
to develop.
     What is the point of studying towns in this way? For me, it is simply that one gets greater pleasure by
visiting and seeing a town with one's own eyes. A personal visit to a town may help one better understand
why it is attractive   10  just reading about it in a guide-book.

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单项选择题