Final answer:
The complex sentence in the given options is: "When it snows this hard, most schools in the area close for the day."
Step-by-step explanation:
The complex sentence in the given options is: When it snows this hard, most schools in the area close for the day.
A complex sentence is a sentence that contains an independent clause and one or more dependent clauses. In this sentence, the independent clause is "most schools in the area close for the day" and the dependent clause is "When it snows this hard". The dependent clause cannot stand alone as a sentence because it relies on the independent clause to make complete sense.