A subseasonal weather forecast attempts to predict weather conditions three to four weeks in blank its predictions are therefore more short-term than those of the seasonal forecast, which attempts to predict the weather more than a month in advance.
Which choice completes the text so that it conforms to the conventions of Standard English?
advance,
advance
advance;
advance and
Choice C is the best answer. The clause “A subseasonal…advance” and the clause “its predictions…forecast” are both independent clauses, so using a semicolon to separate them is grammatically correct.
Choice A is incorrect. This choice creates a run-on sentence error. The clause “A subseasonal…advance” and the clause “its predictions…forecast” are both independent clauses, so a comma is not enough to separate them. Choice B is incorrect. This choice creates a run-on sentence error. The clause “A subseasonal…advance” and the clause “its predictions…forecast” are both independent clauses, so they need to be separated with specific punctuation (a period, a semi-colon, a colon, a dash, or a comma + a coordinating conjunction). Choice D is incorrect. This choice creates a run-on sentence error. The clause “A subseasonal…advance” and the clause “its predictions…forecast” are both independent clauses, so the word “and” by itself is not enough to separate them. There would need to be a comma before “and” for this choice to work.