Explanation
Correct answer: A.
Choice A is the best answer. “Nine months…offense” and “according to…system” are both independent clauses. Separating them with a period and turning them into their own sentences is the only grammatically correct choice among the provided options.
Why the other choices are wrong
Choice B
Choice B is incorrect. This choice results in a comma splice error, which is a punctuation error that occurs when two independent clauses are joined by only a comma. “Nine months…offense” and “according to…system” are both independent clauses, so they need to be either joined by a semicolon, joined by a comma and a coordinating conjunction, or separated by a period.
Choice C
Choice C is incorrect. This choice results in a run-on sentence, which occurs when two independent clauses are joined without punctuation. “Nine months…offense” and “according to…system” are both independent clauses, so they need to be either joined by a semicolon, joined by a comma and a coordinating conjunction, or separated by a period.
Choice D
Choice D is incorrect. This choice results in a run-on sentence, which occurs when two independent clauses are joined without punctuation. “Nine months…offense” and “according to…system” are independent clauses, so we would need to put a comma before the coordinating conjunction “and” to join them properly.