Dear Robert,

How time files! The happy days we shared often shines in my memory . As you know, my college entrance exam is approaching, which also announces the end of this sort of pressing study life. However, I intend to have a meaningful summer vacation. First, I will learn to drive to get a driving license, which is a new activity for a high school graduate in China. I will have a good rest, enjoying my hobbies. With the computer becoming more and more important, I will take some English communication ability I. After that, I Will pay a visit to some tourist attractions to widen my horizon.

That is the plan for my vacation. I am looking forward to being told about your arrangements of vacation. Give me your quick reply soon, OK?

Best wishes!　

80. √　 81.That　 What　 82.of后加the　 83.去掉with　 84.去掉had　 85.and　　　　　　 but

76.go　 going　 77.extreme　 extremely　 78.every　　　 either/each　 79.house　　 houses

73.unfortunate/unlucky　sulted　 75.shabby/worn

66、selfishness　 67.shadow　 68.admit　 69.dictation　 70.adopt　 71.patience　 72.devotion

1-10DCBDA CBDCA　 11-20ADBBA CCBAD　 21-30CBADA CADBD

31-40CABCB DBBCB 41--50DACCA DBCBA　 51-60CACDA CDBCA

61-65GACDB

18. 经检测汽车A的制动性能：以标准速度20m/s在平直公路上行使时，制动后40s停下来。现A在平直公路上以20m/s的速度行使发现前方180m处有一货车B以6m/s的速度同向匀速行使，司机立即制动，能否发生撞车事故？

17．如图所示，一平直的传送带以速度＝2m/s匀速运动，传送带把A处的工件运送到B处，A、B相距L＝10m，从A处把工件无初速地放到传送带上，经过时间t＝6s，能传送到B处，欲用最短的时间把工件从A处传送到B处，求传送带的运行速度至少多大？

16．“10米折返跑”的成绩反映了人体的灵敏素质．测定时，在平直跑道上，受试者以站立 式起跑姿势站在起点(终点)线前，听到起跑的口令后，全力跑向正前方10米处的折返线，测试员同时开始计时．受试者到达折返线处，用手触摸折返线处的物体(如木箱)后，再转身跑向起点(终点)线，当胸部到达起点(终点)线的垂直面时，测试员停止计时，所用时间即为“10米折返跑”的成绩，如图所示．设受试者起跑的加速度为4 m/s²，运动过程中的最大速度为4 m/s，快到达折返线处时需减速到零，减速的加速度为8 m/s²，返回时达到最大速度后不需减速，保持最大速度冲线．求该受试者“10米折返跑”的成绩为多少？

15．如图所示，物体A、B的质量均为m，通过定滑轮用细绳相连，物体B所接触的面是竖直的，且细绳的OB段竖直、OA段水平，设物体与接触面间的动摩擦因数均为，滑轮的摩擦不计.欲使物体A在水平面上做匀速直线运动，则水平施于物体A的力F应为多大？