When we read the question, our ears prick up at the strong language in the phrase "without any loss of efficiency." Quite possibly, the rest of the argument could be true (as we take it to be, as evidence) and there could be some loss of efficiency. That will be our prediction. More specifically, the question asks for a strengthener, we will look for an answer choice like, "We won't lose efficiency from the change."
Testing this prediction, our prediction involves imagining the future state, but choices (B), (D), and (E) are all relevant only to the state of affairs before the change. Choice (C) weakens the plan, by giving a reason to that the cost and/or efficiency may worsen.That leaves us only with (A).
We can look for logical confirmation of the correct answer: we apply the negation test to (A). Say citizens who visit the offices do require the use of fax machines. Then removing the fax machines would result in a loss of efficiency.
The correct answer is (A).