Explanation
Correct answer: B.
Choice B is the best answer. "However" is used to indicate a contrast between two ideas. The first sentence describes how Still used to be famous. This sentence describes how Still is not very famous today, so the transition "however" fits perfectly.
Why the other choices are wrong
Choice A
Choice A is incorrect. This choice uses a transition that introduces an example. But the second sentence doesn’t provide a specific example of Still’s famous contributions to the Underground Railroad. Instead, it changes the subject to how his fame has faded over time.
Choice C
Choice C is incorrect. This choice uses a transition that introduces an example or continuation of a previous idea. But the second sentence doesn’t provide a specific example of Still’s famous contributions to the Underground Railroad. Instead, it changes the subject to how his fame has faded over time.
Choice D
Choice D is incorrect. This choice uses a transition that indicates the agreement between two ideas. But this sentence shows a contrast with the first sentence—namely, that Still used to be very famous but now isn’t very famous.