A recent report determined that although only 3 percent of drivers on Maryland highways equipped their vehicles with radar detectors,33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly,drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assupmtions?

A Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers tho do not.

B Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

C The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.

D Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.

E Drivers on Maryland highways exceeded the speed limit more often than did driveres on  other state highways not covered in the report.

答案是b, 我按排除法可以做出来，但是这道题的逻辑我却很晕，是不是需要用集合知识来划一下啊？ 请各位大牛帮助划一下简图好吗？？thanks!!!!!

(1)3%的车装探测器.A1

(2)被罚的超速车中33%装探测器.A2

结论装探测器的比不装的更倾向于超速.B

问必要条件:

使前因后果能连接起来.

被罚的人比不被罚的人更愿意超速.

A1的比率小于A2.推出被罚的车中多数人装探测器.从这个中间结论和结论之间的关系就能寻找到必要条件了.