Which choice completes the text so that it conforms to the conventions of Standard English?
A
libraries train
B
libraries: train
C
libraries—train
D
libraries, train
Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is the punctuation of items in a simple series. The comma after "libraries" is used conventionally to separate the first and second items ("libraries" and "train stations") in the series.
Why the other choices are wrong
Choice A
Choice A is incorrect because it fails to separate the first two items ("libraries" and "train stations") in the series.
Choice B
Choice B is incorrect because a colon can’t be used in this way to separate items in a simple series.
Choice C
Choice C is incorrect because a dash can’t be used in this way to separate items in a simple series.