求助：prep-1-20。前人prep题没有标号，找不到讨论帖。

20.
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For years the beautiful Renaissance buildings in Palitito have been damaged by exhaust from the many tour buses that come to the city.  There has been little parking space, so most buses have idled at the curb during each stop on their tour, and idling produces as much exhaust as driving.  The city has now provided parking that accommodates a third of the tour buses, so damage to Palitito's buildings from the buses' exhaust will diminish significantly.

Which of the following, if true, most strongly supports the argument?

(A) The exhaust from Palitito's few automobiles is not a significant threat to Palitito's buildings.

(B) Palitito's Renaissance buildings are not threatened by pollution other than engine exhaust.

(C) Tour buses typically spend less than one-quarter of the time they are in Palitito transporting passengers from one site to another.

(D) More tourists come to Palitito by tour bus than by any other single means of transportation.

(E) Some of the tour buses that are unable to find parking drive around Palitito while their passengers are visiting a site.

答案c。不明白。。。

旅游车一般用1/4时间运送旅客，那么，其余3/4是不运送的，如果没有足够的PARKING， 它们会一直idle,有了比较多的停车位，它们就可以熄火，这样会大大减少废气排放.

另外看其他的解释都不对，也只有C 了，不知道这样解释对吗

二楼的解释已经很好，只是不应有熄火一说。

很简单，originally, a bus  spends 1/4 of the time doing transportation, while spending 3/4 of the time poluting the buildings. Now, with a parking space, it will spend  3/4 of time in the parking lot instead.==> polution to the buildings will go down.

狀況：旅遊巴士因為沒有停車位，只好在路邊 idling 等待遊客，此舉產生與開車時一樣多的廢氣污染建築。方案：提供更多車位

(A)與題目矛盾...(且如為真則傾向 weaken)

(B)irrelevant

(C)旅遊巴士只有1/4的時間是輸送旅客（亦即其他3/4的時間是idling）故如有停車位，則巴士不需要idling了。僅在需要輸送旅客時(driving)才會產生廢氣 => Support

(D)irrelevant

(E)irrelevant. 題目討論的是一般性，而本選項 "some of the tour buses"為特殊狀況，不代表一般現象。此外，題目討論的是如何減少idling 產生的污染，而不是討論車子行駛時造成的廢氣。

why d is irrelevant?

if people come here by car, then the pollution will increase

我這邊的 irrelevant 是指對題目 weaken/support 過程並無影響。

你必須自己加入許多猜測或假設使D成立，比方你說的"if people come here by car, then the pollution will increase"

但這在做GMAT是不允許加入個人的假設的 就算是常識或是讀者熟悉的背景知識

僅能就題目給定的範圍來答題

事實上 你也可以假設 D 選項大家都是走路來的 那不是反而會減少污染嗎? 那到底D選項 weaken or support？

像這樣自己加入新條件才能解釋的 一般不能作為答案選項

畢竟誰能保證每個人自己加入的條件都一樣呢？

個人意見供參考