Final answer:
The sentence that only has a main clause is A Before the storm hit, we tied down the outdoor furniture.
Step-by-step explanation:
The sentence that only has a main clause is A Before the storm hit, we tied down the outdoor furniture. A main clause is a complete thought that can stand alone as a sentence. In this sentence, the main clause is 'we tied down the outdoor furniture.' It expresses a complete idea and does not rely on any other clauses.
Learn more about main clauses in sentences