This question is asking you to determine which answer is LEAST likely to help determine whether the passage's argument is practical. Therefore, there may be other answers that you think are not likely to help, but you're looking for an answer that is clearly unrelated or not relevant.
(B) is correct because the statement is irrelevant. The passage deals with sewage sludge being turned into oil, whereas the answer deals with sewage sludge being turned into water.
(A) is incorrect. The passage argues that new technology should allow us to produce energy is an environmentally friendly manner. This answer choice brings up the consideration of how environmentally friendly dumping sewage sludge is. Therefore, it is relevant to whether there are environmental effects from this new tech.
(C) is incorrect. It is possible that economic considerations are relevant in evaluating the practicality of the passage's proposal.
(D) is incorrect. This answer is similar to A in that it deals with the environmental effects of the new technology.
(E) is incorrect. This answer deals with the potential waste that would be produced from the new technology. This could be relevant to evaluating the passage's proposal.