人说话时发出的声音是靠 ；蜜蜂飞过我们身边时，常听到一阵“嗡、嗡、嗡“的声音，这声音是蜜蜂翅膀 而产生的．
声带振动；振动．
The town of Greenfield recently instituted a substantial supplementary tax on all households, whereby each household is taxed in proportion to the volume of the trash that it puts out for trash collectors to pick up, as measured by the number of standard-sized garbage bags put out. In order to reduce the volume of the trash on which their tax bill is based, Greenfield households can deliver their recyclable trash to a conveniently located local commercial recycling center, where such trash is accepted free of charge. The supplementary tax provides some financial incentive to Greenfield households to do each of the following EXCEPT
A．sort out recyclable trash thoroughly from their other trash.
B．dump nonrecyclable trash illegally at parks and roadsides.
C．compress and nest items of nonrecyclable trash before putting them out for pickup.
D．deliver recyclable materials to the recycling center instead of passing them on to neighbors who want to reuse them.
E．(E) buy products without packaging or with recyclable rather than nonrecyclable packaging.
水利水电工程施工总承包二级企业可以承担的施工项目有（）
A.库容0．9亿m3的水库
B.库容1．5亿m3的水库
C.装机容量100MW的电站
D.装机容量200MW的电站
E.单项合同额不超过企业注册资本金5倍的各种类型水利水电工程
