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的名称是“此面禁用手推车”。（）
举一反三
【单选题】Entertainment in LondonBuying Books Londoners are great readers. They buy vast numbers of newspapers and magazines and even of books especially paperbacks, which are still comparatively cheap in spite...
A.
It’s to the cast of London.
B.
It’s street of bookstores.
C.
It’s a center for second-hand books.
D.
It’s where worthless books are sold.
【单选题】图示梁上，先加P 1 ，A、B两点挠度分别为△ 1 、△ 2 ，再加P 2 ，挠度分别增加△' 1 和△' 2 ，则P 1 做的总功为______。
A.
P 1 △ 1 /2
B.
P 1 (△ 1 +△' 1 )/2
C.
(△ 1 +△' 1 )/2
D.
P 1 △ 1 /2+P 1 △' 1