Which choice completes the text so that it conforms to the conventions of Standard English?
A
world but
B
world, but,
C
world,
D
world, but
Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is the coordination of main clauses within a sentence. This choice correctly uses a comma and the coordinating conjunction "but" to join the first main clause ("At...world") and the second main clause ("the...longer").
Why the other choices are wrong
Choice A
Choice A is incorrect because when coordinating two main clauses such as these, it’s conventional to use a comma before the coordinating conjunction.
Choice B
Choice B is incorrect because a comma isn’t needed after the conjunction "but."
Choice C
Choice C is incorrect because it results in a comma splice. Without a conjunction following it, a comma can’t be used in this way to join two main clauses.