Answer:
Although the dentist found nothing wrong with Sue's teeth,she still had a toothache so she went to bed
Step-by-step explanation:
A complex sentence is a sentence with one independent clause and at least one dependent clause. An independent clause is a clause that can stand on its own as a complete sentence, while a dependent clause is a clause that cannot stand on its own and needs another clause to make sense. A dependent clause usually starts with a subordinating conjunction, such as because, since, if, until, when .Based on this definition, the complex sentence among the options is: Although the dentist found nothing wrong with Sue's teeth, she still had a toothache, so she went to bed. This sentence has one independent clause (she still had a toothache) and two dependent clauses (Although the dentist found nothing wrong with Sue's teeth and so she went to bed). The dependent clauses start with the subordinating conjunctions although and so. The other sentences are either simple sentences (one independent clause) or compound sentences (two or more independent clauses joined by a coordinating conjunction).