The new oval bike gears, which allow a rider to transfer fifty percent more energy to forward motion when compared to traditional bike gears, allows a rider to travel more miles at faster speeds with less fatigue. For this reason, if Speedy delivery replaces all of it's traditional bike gears with the new oval gears, its bike messengers will be able to deliver more packages in a day.

Which one of the following, if true, would most weaken the conclusion drawn above?

A) Bike messengers generally prefer traditional bike gears over the new oval bike gears.

B) The area within which Speedy deliver delivers packages is uneven terrain which is difficult for bike riders to traverse.

C) Bike messengers will require costly training to learn how to use the new oval bike gears.

D) The area within which Speedy delivery delivers packages has a bike speed limit which is lower than the peak speed of bikes with traditional gears.

E) Oval gears are much more expensive than traditional gears.

OA is D
I will concur to the validity of option A but does that mean that option e could not be the answer. Because the question didn't talk about price. I need an Expert explanation on this.