Explanation
Correct answer: D.
Choice D is the best answer. The sentence makes and supports a generalization about the effect of redesigning a city flag, noting that redesigning a city flag can create a meaningful symbol of civic pride, as was the case when the city of Pocatello redesigned its flag.
Why the other choices are wrong
Choice A
Choice A is incorrect because the sentence explains that many US cities have redesigned their flags and provides an example; it doesn’t make and support a generalization about the effect of redesigning a city flag.
Choice B
Choice B is incorrect because the sentence provides an example of a city that redesigned its flag; it doesn’t make and support a generalization about the effect of redesigning a city flag.
Choice C
Choice C is incorrect because the sentence emphasizes why the flag of Pocatello was redesigned; it doesn’t make and support a generalization about the effect of redesigning a city flag.