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图1表示生态系统中各成分之间的联系，图2为一定时间内某一生态系统中的几个种群数量变化曲线，请据图回答

某地区因环境污染造成E中出现大量白化苗，对F、D数量的影响是（）

答案

参考答案：F、D数量都将减少

单项选择题

英国社会救助制度采取的方式为( )

A．生活救助金

B．社会保险

C．生活补贴

D．生存保证金
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单项选择题

Both bus and tree topologies are characterized by the use of multipoint （） . For the bus, all stations attach, through appropriate hardware （） known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received fromthe （） . A transmission from any station propagates the length of the medium in both directions and can be received by all other （） . At each end of the bus is a （） , which absorbs any signal, removing it from the bus.

Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received fromthe（）.

A．tree

B．bus

C．star

D．ring
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