求助，第2版verbal CR第5题的D选项为什么不选？

babyapple127

求助！！无法理解

passme

Since the mayor’s publicity campaign for Greenville’s
bus service began six months ago, morning automobile
traffi c into the midtown area of the city has decreased
7 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 5 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 satisfi ed with the Greenville bus service
than they were before the mayor’s publicity
campaign began.

你说这个题吧
题里说campaign是半年以前的。问题主要针对是否因为campaign才有了后来的改变。
一年前---------六个月前:campaign----------现在
D说现在bus的量和一年前一样。。。
所以这样的话，改变与campaign无关。

HarrisZheng

C是它因

D不能weaken， 即便公交数量没变 也不表示乘车的人没变 满载的车跟空载的车能一样么？