原子序数小于18的八种连号元素，它们的单质熔点随原子序数增大而_爱下问搜题

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问题选择题

原子序数小于18的八种连号元素，它们的单质熔点随原子序数增大而变化的趋势如图所示，图中X元素应属于

A．ⅢA族

B．ⅣA族

C．ⅤA族

D．ⅥA族

答案

答案：B

根据图像可知，X的熔点最高，在短周期元素中，应该是第ⅣA族的碳元素形成的金刚石，所以答案选B。

完形填空

完形填空。

     Life today is    1   than it was hundreds of years ago, but it has    2   some new problems. One of the
biggest problems is pollution. We can see it, smell it, drink it, and    3   hear it.
        4   has polluted Earth. The more people, the more .because there were not    5   people. Now man is
slowly polluting    6   world.
     Air pollution is still the most serious among (在……之中) all kinds of pollution. It is bad for all    7
animals. It is caused by heavy traffic. It is said that the situations will be much better if people ride bikes
   8   driving cars. When you are riding, there is no pollution. But even in developing countries, most
people don't go to work by bike. It is not because bikes are expensive or people are tired if they ride to
work, but because the roads for the cars become    9 , more people put away their bikes and go to work
by car or by bus, then things are getting    10   .

(    )1. A. happy
(   )2. A. take
(    )3. A. but
(   )4. A. Man
(    )5. A. too much
(    )6. A. the whole
(    )7. A. live
(    )8. A. and
(    )9. A. better
(    )10. A. better and better

B. harder
B. taken
B. even
B. A man
B. much too
B. whole the
B. alive
B. because of
B. harder
B. worse and worse

C. easier
C. bring
C. however
C. Persons
C. so many
C. the all
C. lively
C. but
C. well
C. the better; the better

D. more hardly
D. brought
D. if
D. A person
D. so much
D. all the
D. living
D. instead of
D. worse
D. the worse; the worse

单项选择题

图示结构的M图中B点的弯矩是（）。

A.零

B.内侧受拉

C.外侧受拉

D.以上三种都有可能