请教L2003-10-C-20

20. On some hot days the smog in Hillview reaches unsafe levels, and on some hot days the widn blows into Hillview from the east. Therefore, on some days when th wind blows into Hilllview from the east, the smog in Hillview reaches unsafe level.

The reasoning in the argument is flawed in that the argument

正项

B) fails to recognize that one set might have some members in common with each of two others even though those two other sets have no members in common with each other.

这道题为什么是Flawed ? B）为什么涉及3个set, 还有和in common 有什么关系？

这题我也做错了，不过看了答案想明白了

3个set应该就是：some hot days, the smog in H reaches unsafe levels, wind blows into H from the east.

one set might have some members in common with each of two others, 这句就解释了，some hot days分别与smog和wind have members in common，有交集因为both smog and wind occur on some hot days.但这不代表，smog and wind 之间也有交集，两者可能并不发生在一起

不知说明白了没有。

明白了，thx~