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 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 satisfied with the
Greenville bus service than they were before the mayor’s publicity campaign
began.

Got stumped by the answer. Option C specifically says road construction reduced number of lanes available to commuters (not to automobile traffic). May be footpaths were closed but the space for cars was the same. Then how come that weaken the conclusion?

Also, in case of option D, if number of buses remained same, then its perhaps the increase in population that has caused the rise in bus riding people and not the Mayor’s plan. Doesn’t this weaken the conclusion more than option C ?