题目

如图甲所示，劲度系数为k的轻弹簧竖直放置，下端固定在水平地面上。一质量为m的小球，从距弹簧上端高h处由静止自由释放，在接触到弹簧后继续向下运动。若以小球开始下落的位置为原点，竖直向下建立坐标轴Ox，则小球的速度平方v2随坐标x的变化图象如图乙所示。其中OA为直线，并与平滑曲线ABC相切于A点；B点为曲线最高点。设小球的位置坐标为x，小球所受重力的瞬时功率为P，弹簧的弹性势能为EP。则下列判断正确的是（    ）        A．对阅读理解。     A million motorists leave their cars filled up with petrol and with the keys in the ignition (点燃) every day.The cars are sitting in petrol stations while drivers pay for their fuel. The Automobile Association(A.A) hasdiscovered that cars are left unattended for an average three minutes and sometimes longer as drivers buy drinks, sweets, cigarettes and other consumer items.With payment of credit cards becoming more and morecommon, it is not unusual for a driver to be out of his car for as long as six minutes, providing the car theft with a golden opportunity.      For more than ten years there has been a big rise in car crime than in most other types of crime. An averageof more than two cars a minute are broken into or stolen in the UK. Car crime accounts for almost a third of all reported offenses with no signs that the trend is slowing down.      Although there are highly professional criminal involved in car theft, almost 90 percent of car theft is committed by the opportunists. Amateur thieves are aided by our own carelessness. The A.A. recommendslocking up whenever you leave the car and for however short a period. A partially open sunroof or window isa further come-on (诱惑) to thieves.      There are many other traps to avoid. The A.A. has fond little awareness among drivers about safe parking. Most motorists questioned made no efforts to avoid parking in quiet spots-just the places thieves love. The A.A.advises drives to park in places with people around because thieves don't like audiences. 1. We can learn from the passage that _____. A. there is an increasingly large number of car crimes in the UKB. about 20% of all reported crimes involve cars C. car crime is decreasing gradually D. the A. A. didn't pay much attention to car crimes 2. The underlined word "opportunists" in this passage most probably refers to _____. A. people who take chances to steal into carsB. people who always steal or break into carsC. highly skillful criminals D. careless criminals who tend to fail in their crimes 3. The A. A, suggests that the car owners should _____. A. always lock up their cars when they leave B. keep the sunroof and windows open C. avoid parking in crowded places D. keep some people around to watch their cars 4. Paragraph Three mainly talks about _____. A. the professional car criminals B. the opportunities for non-professional car thieves C. the anti-theft tipsD. when to lock the car