Recycling is preferable to incineration and dumping in landfills.
Recycling is profitable too.

Proposal: Legislator proposes that communities should be required to adopt recycling and to reach the target of recycling 50 percent of all solid waste within 5 years.

We need to question the proposal i.e. what would question the advisability of implementing the proposal? The thing that comes to my mind is that a 50% limit has been set. What if 50% things are not recyclable?

(A) Existing recycling programs have been voluntary, with citizen participation ranging from 30 percent in some communities to 80 percent in others.
Just because existing programs are voluntary, it does not mean that all communities should not be required to adopt now. If the proposal has enough merits, perhaps making it compulsory may be a good idea.

(B) Existing recycling programs have been restricted to that 20 percent of solid waste that, when reprocessed, can match processed raw materials in quality and price.
This is as per our pre-thinking. Existing programs have been restricted to 20% since only 20% can match processed raw materials in quality and price. So achieving 50% may not be possible.

(C) Existing recycling programs have had recurrent difficulties finding purchasers for their materials usually because of quantities too small to permit cost-effective pickup and transportation.
Right now, the quantities are too small to work out. If recycling becomes mandatory, it is possible that the current difficulty of finding purchasers will be sorted since the quantities are bound to increase. Hence, this is no reason to not establish the program. The program may actually resolve this difficulty.

(D) Some of the materials that can be recycled are the very materials that, when incinerated, produce the least pollution.
It doesn't matter that these materials produce least pollution. If they are recycled, they produce no pollution.

(E) Many of the materials that cannot be recycled are also difficult to incinerate.
What happens to materials that cannot be recycled is irrelevant.

Answer (B)