Explanation
Correct answer: A.
Choice A is the best answer. This sentence emphasizes just how far maglev advocates’ dreams are from coming true. “In fact” is a transition used to emphasize the truth of a statement that modifies the previous statement and therefore fits perfectly in this context.
Why the other choices are wrong
Choice B
Choice B is incorrect. This choice uses a cause-and-effect transition, which doesn’t make sense here. Maglev advocates’ dream remaining unrealized would not cause there to be only a few maglev trains, all located in Asia.
Choice C
Choice C is incorrect. This choice uses a disagreement transition, which doesn’t make sense here. In fact, this sentence agrees with the previous sentence—both talk about how maglev trains are far from becoming common in the US.
Choice D
Choice D is incorrect. This choice uses a disagreement transition, which doesn’t make sense here. In fact, this sentence agrees with the previous sentence—both talk about how maglev trains are far from becoming common in the US.