Explanation
Correct answer: B.
Choice B is the best answer. The first sentence makes the claim that using grime-eating bacteria has led to “impressive results.” This sentence supports that claim by describing the specific findings of the biologists’ experimentation. The transition “in many cases” fits the context perfectly.
Why the other choices are wrong
Choice A
Choice A is incorrect. This choice uses a disagreement transition. But this sentence actually agrees with the previous sentence. Both claim that grime-eating bacteria are better at cleaning artworks than chemicals.
Choice C
Choice C is incorrect. This choice uses a cause-and-effect transition, which doesn’t make sense in context. The fact that the results of the experimentation have been impressive overall doesn’t cause the bacteria to have proven more effective.
Choice D
Choice D is incorrect. This choice uses a transition that indicates the addition of a new idea. But this sentence doesn’t introduce a new idea. Instead, it elaborates on the same idea laid out in the previous sentence by describing the “impressive results” in more detail.