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【单选题】
适用于运行速度在2.5m/s以下电梯的减速器为（）。A.
蜗杆蜗轮式减速器
B.
双蜗杆减速器
C.
直齿轮式减速器
D.
无齿轮减速器
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反馈参考答案：
举一反三
【单选题】.The teacher recommended that every student England party.
A.
took active part in
B.
takes active part in C . take active part in D. would take active part in
【单选题】Answer the questions about the words. 2 In an atmosphere of political radicalism, will students be (a) active, or (b) not very active?
A.
active
B.
not very active
【简答题】寄生物与宿主的协同进化
【单选题】A knowledge of the composition of the weed community ______.
A.
is essential to the efficient control of weeds
B.
may lead us to be aware of the fact that the soil contains enormous quantities of seeds of numerous species
C.
helps us to have a good idea of why seeds can lie dormant for years
D.
provides us with the means to identify weeds at the seedling stage
【简答题】active absorption
【单选题】The ratio of the work done by the machine ______the work done on it is called the efficiency of the machine.
A.
against
B.
with
C.
to
D.
for
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