Explanation
Correct answer: A.
Choice A is the best answer. The convention being tested is the punctuation of a supplementary word or phrase between two main clauses. This choice correctly uses a comma to separate the supplementary adverb “however” from the preceding main clause (“Okinaka doesn’t…single-handedly”) and a semicolon to join the next main clause (“all…culture”) to the rest of the sentence. Further, placing the semicolon after “however” correctly indicates that the information in the preceding main clause (Okinaka doesn’t make such decisions single-handedly) is contrary to what might be assumed from the information in the previous sentence (Okinaka sits on the review board that adds new sites to the Hawaii Register of Historic Places).
Why the other choices are wrong
Choice B
Choice B is incorrect because placing the semicolon after “single-handedly” and the comma after “however” illogically indicates that the information in the next main clause (all historical designations must be approved by a group of experts) is contrary to the information in the previous clause (Okinaka doesn’t make such decisions single-handedly).
Choice C
Choice C is incorrect because it results in a comma splice. Commas can’t be used in this way to punctuate a supplementary word or phrase between two main clauses.
Choice D
Choice D is incorrect because it results in a run-on sentence. The two main clauses are fused without punctuation and/or a conjunction.