某地区每小时最大降雨量H=150mm/h，现设计一栋楼房，屋面水平集水面积为1000m2，现选用管径为10cm的落水管，则至少需要设置落水管( )根。
A．4
B．5
C．6
D．7
参考答案：A
解析：
屋面落水管的布置量与屋面集水面积大小、每小时最大降雨量、排水管管径等因素有关，关系如下：
F=438 D2/H
式中 F——单根落水管允许集水面积(水平投影面积，m2)；
D——落水管管径(cm，采用方管时面积可以换算)；
H——每小时最大降雨量(mm/h，由当地气象部门提供)。
则：F=438×102/150=292(m2)，屋面落水管的布置量=1000/292=3.42，所以选择4根。
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| The smell of old, dusty books reminds me of my father. An avid (贪婪的) 1 , he had many books, most of which went unread. He owned books on 2 from medicine to Vietnam to several sets of encyclopedias (百科全书). When I enter one of his 3 bookshops, such as Powell's, I am 4 back to a time when the two of us were 5 . I see him standing by a shelf, 6 through a medical magazine, or opening his wallet to pay for yet 7 book, knowing full well that Mom would 8 him on"wasting money on books you never 9 !" Walking past rows and rows of books in our study, I remember 10 , after the cancer struck, he came less and less and read fewer and fewer books. They became just part of the 11 , collecting only dust and 12 . Near the end, perhaps knowing he would never get to read them all, he gave almost all of the books away, 13 only a few. He treated them with an almost holy (神圣的) reverence (崇敬), 14 any crease (皱褶) or damage would destroy them totally. 15 was the man who would neglect a huge coffee mark, replaced by one who would get 16 suddenly at a small crease. I have read a few now, after he died, and each time it causes a 17 . But I suppose it is a kind of quest (追求), because if I can take on his thirst for 18 , cheerful smile, and willingness to help others, then like a match in the 19 , I will bring a little light into the world. And if that light touches others, maybe it will spread far and 20 , to light up the heavens. I think he'd like that. | ||||
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