Answer:
Therefore, the correct answer is B: "A dependent clause is followed by an independent clause."
Step-by-step explanation:
The structure of this complex sentence is dependent clause + independent clause.
A dependent clause is a clause that cannot stand on its own as a complete sentence because it does not express a complete thought. A dependent clause often begins with a subordinating conjunction, such as "once," "because," or "although."
An independent clause is a clause that can stand on its own as a complete sentence because it expresses a complete thought.
In this sentence, the dependent clause "once the storm subsided" modifies the independent clause "a simple spring day had become the worst day in recent memory." The dependent clause specifies the time frame in which the action in the independent clause occurred.