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.

OA after some discussion...