质量为m的跳水运动员，从离水面高h的跳台上以速度v1斜向上跳起，跳起的最大高度为

IEEE 802.3u标准是对802.3的物理层作了调整，其目的是使得物理层在实现100Mbps速率时所使用的传输介质和信号编码方式的变化不会影响______。

A．LLC子层

B．网络层

C．MAC子层

D．传输层

作图：（1）如图1所示，人的手臂相当于一个杠杆，它的支点在O点．请画出图中铅球对手的作用力F的力臂L；

（2）如图2所示，请根据小磁针的指向在图中标出电源的正、负极．

Why is ______ fun. What delights may its practitioner expect as his reward. First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design. Second is the pleasure of making things that are useful to other people. Third is the fascination of fashioning complex puzzle-like objects of interlocking moving parts and watching them work in subtle cycles, playing out the consequences of principles built in from the beginning. Fourth is the joy of always learning, which springs from the ______ nature of the task. In one way or another the problem is ever new, and its solver learns something: sometimes ______, sometimes theoretical, and sometimes both. Finally, there is the delight of working in such attractable medium. The ______, like the poet, works only slightly removed from pure thought-stuff. Few media of creation are so flexible, so easy to polish and rework, so readily capable of realizing grand conceptual structures.
Yet the program ______, unlike the poet’s words, is real in the sense that it moves and works, producing visible outputs separate from the construct itself．It prints results, draws pictures, produces sounds, moves arms．Programming then is fun because it gratifies creative longings built deep within us and delights sensibilities we have in common with all men．

A．programming
B．composing
C．working
D．writing

过度训练综合征处理的重点是（）。

A、早期发现

B、及时治疗

C、消除病因，调整训练

D、药物治疗

电缆支架的安装有何要求？电缆的敷设完毕应在哪些地方固定？