This argument proceeds by saying the reason most children taking advantage of this program belong to affluent families is that most low-income families are not aware of the program.
We are looking for another reason that might cause the low income families to not take advantage of this program--which means the original reason the argument identified may not be true.
(a) is not a reason low income families don't take advantage--in fact the program lowers tuition fees so this would make them more likely to take advantage
(b) yes, since the friends and families of low income families don't pay any state tax, they wouldn't be able to donate any of it. This is a likely reason they don't take advantage of the program.(c) Since the cost of lunch is higher, low income families may not want to take advantage of the program, but this is not super strong, as the prices are only fractionally higher.
(d) Again, this is a very weak reason to not take advantage of the program, as the transition program is mentioned to be short.
(e) This is not another reason low income families didn't take advantage of the program. In fact, this might even support the original reason (low-income families were not aware of the program because they didn't see the flyers)
(b) is the right answer