写出综合布线的组成系统
参考答案：
工作区子系统、水平区子系统、垂直干线子系统、管理子系统、设备间子系统楼宇（建筑群）子系统。
During a home visit 4 days after delivery, the breast-feeding client tells the nurse that her breasts are hard and tender. The nurse suspects breast engorgement. Which of the following action should the nurse instruct the client to do
A. Take a moderately p analgesic after the infant breast-feeds on both sides.B. Use her hand or a pump to express a small amount of breast milk before breast-feeding.C. Discontinue breast-feeding immediately and replace it with bottle-feeding during the night.D. Apply ice packs to the breasts for 20 minutes just before breast-feeding the newborn.
如图所示，质量．M=4kg的滑板曰静止放在光滑水平面上，其右端固定一根轻质弹簧。弹簧的自由端C到滑板左端的距离L=0．5 m，这段滑板与木块彳（可视为质点）之间的动摩擦因数μ=0．2，而弹簧自由端C到弹簧固定端D所对应的滑板上表面光滑．小木块以速度v0="10" m／s由滑板左端开始沿滑板a表面向右运动．已知木块a的质量m="l" kg，g取10m/s2．求：
①弹簧被压缩到最短时木块A的速度；
②木块A压缩弹簧过程中弹簧的最大弹性势能．
