sat suite question viewer
Materials scientist Marie-Agathe Charpagne and her colleagues believed they could improve on the multicomponent alloy NiCoCr, an equal-proportions mixture of nickel (Ni), cobalt (Co), and chromium (Cr), by replacing chromium with ruthenium blank the alloy that resulted, NiCoRu, turned out to be an unsuitable replacement for NiCoCr.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Choice D is the best answer. The convention being tested is the coordination of main clauses. This choice correctly uses a comma and the coordinating conjunction “but” to join the first main clause (“Materials…Ru”) and the second main clause (“the alloy…NiCoCr”).
Choice A is incorrect because it results in a run-on sentence. The two main clauses are fused without punctuation and/or a conjunction. Choice B is incorrect because when coordinating two longer main clauses such as these, it’s conventional to use a comma before the coordinating conjunction. 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.