I think option B is the required assumption here.
The argument says:
• highway maintenance is currently paid entirely by toll revenue
• highways still must be maintained
• therefore, if tolls are eliminated, the entire maintenance cost will have to come from increased general taxes
But there is a hidden assumption in that jump.
The author is assuming that eliminating tolls would NOT free up enough money from toll collection operations to cover any meaningful part of the maintenance costs.
That is exactly what option B says.
If B were false, then the argument weakens immediately because the money saved from removing toll booths, toll workers, collection systems, etc. could help pay for maintenance without needing the full increase in taxes.
So B is necessary for the conclusion to hold.
---
Why the other options do not work:
(A) The argument never says maintenance money must already be collected before work begins.
That issue is completely outside the logic of the argument.
(C) Preventive maintenance is irrelevant.
The conclusion is only about where the money will come from.
(D) The argument never compares whether toll funding or tax funding is cheaper overall.
It only discusses replacing the funding source.
(E) This is too strong.
General taxes could still increase for other unrelated reasons even if tolls remain.
So B is the only choice that directly fills the logical gap in the argument.
I mainly solved this by asking:
“What is the author assuming before concluding that ALL maintenance costs must shift to taxes?”
That pointed directly to B.
If anyone sees another way to frame the assumption quickly, feel free to share.
— Rajdeep