预防医学的主要任务描述不正确的是（） A.预防疾病在人群中的流行 B.治疗疾病促进健

已知一足够长斜面倾角为=37°，一质量M=10kg物体，在斜面底部受到一个沿斜面向上的F=100N的力作用由静止开始运动，物体在2s内位移为4m，2s末撤掉力F，（sin37°=0．6,cos37°=0．8，g=10m/s²）求：

小题1:物体与斜面间的动摩擦因数；

小题2:从静止开始运动物体在斜面上的最大位移S。

爱迪生电池在充电和放电时发生的反应：Fe+NiO₂+2H₂O

充电

放电

Fe（OH）₂+Ni（OH）₂，下列对该蓄电池推断错误的是：（　　）

①放电时，Fe参与负极反应，NiO₂参与正极反应

②充电时，阴极上的电极反应式为：Fe（OH）₂+2e^-═Fe+2OH^-

③放电时，电解质溶液中的阴离子向负极方向移动

④放电时，负极上的电极反应式为：Fe+2H₂O-2e^-═Fe（OH）₂+2H⁺

⑤蓄电池的电极必须浸入某种碱性电解质溶液中．

A．③

B．③④

C．④

D．①②⑤

Can Bill _____?[ ]

A. play the chess

B. play the football

C. play the guitar

确认二手车个人汽车贷款额度时所认定的汽车价格是( )。

A．汽车实际成交价

B．汽车实际成交价和贷款银行认可的评估价格中两者的低者

C．汽车实际成交价和贷款银行认可的评估价格中两者的高者

D．贷款银行认可的评估价格

Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept (12) ,examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (13) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.

11（）

A.repeaters

B.relays

C.packages

D.modems