[問題] OG 41

[evelight]

41. Since the mayor's publicity campaign for Greenville's bus service began six months ago, morning automobile traffic into the midtown area of the city has decreased seven percent. During the same period, there has been an
equivalent rise in the number of persons riding buses into the midtown area. Obviously, the mayor's publicity
campaign has convinced many people to leave their cars at home and ride the bus to work.

Which of the following, if true, casts the most serious doubt on the conclusion drawn above?

A. Fares for all bus routes in Greenville have risen an average of five percent during the past six months.
B. The mayor of Greenville rides the bus to City Hall in the city's midtown area.
C. Road reconstruction has greatly reduced the number of lanes available to commuters in major streets leading
to the midtown area during the past six months.
D. The number of buses entering the midtown area of Greenville during the morning hours is exactly the same now as it was one year ago.
E. Surveys show that longtime bus riders are no more satisfied with the Greenville bus service than they were before the mayor's publicity campaign began.

正確答案是C。

這題的其他選項ABDE很明顯都是錯的
可是我不大了解為什麼OG的解釋，除了B以外，幾乎都提到it supports rather than casts doubt on the conclusion.
我覺得ADE的確是錯，但也沒有支持

以下是OG的完整解釋

The passage concludes that the mayor's publicity campaign has persuaded people to ride the bus to word instead of driving, and it cites as evidence the decreased morning automobile traffic and increased bus ridership into the
midtown area. But the road reconstruction described in C provides an alternative explanation for this evidence, so C
is the best answer. A eliminates decreased fares as a possible explanation for the increased ridership, so it supports rather than casts doubt on the conclusion. The fact that the mayor rides the bus, cited in B, may contribute to the
effectiveness of the publicity campaign, but it is irrelevant to assessing whether the campaign caused the increased
ridership. D eliminates a possible explanation-that the increased ridership is a result of extra buses-and thus
supports the conclusion rather than casts doubt on it. E eliminates a possible explanation-that the increased
ridership is a result of improved service-and thus supports the conclusion rather than casts doubt on it.

[evelight]

我在想OG的思路是不是這樣：

ADE在一般狀況下會使搭公車人數減少or沒有影響
但搭乘人數反而增加，表示宣導起作用，故支持結論。

嗯嗯....open to discuss

[Calvin]

evelight, you're right !
ADE的支持，就是排除他因的支持！

排除了「票價-->A」、「公車營運數輛-->D」及「滿意度-->E」等會造成撘乘公車率上昇的可能他因，來支持的確是市長的計劃讓公車搭乘率上昇的！

FYI