Answer:
As Amy read a description of life in San Francisco during the Gold Rush, she imagined the bustling, dusty streets of the city.
Step-by-step explanation:
A complex sentence is one that has an independent clause along with one or more dependent clauses. This means that the independent clause, as well as the dependent clause together, make the complex sentence.
In a complex sentence, the dependent clause starts with a subordinating conjunction. Therefore, among the given sentences, the first sentence contains a subordinating conjunction (as), a dependent clause, and an independent clause.
The second sentence is a compound sentence as it contains a 'coordinating conjunction'.
The third sentence is a simple sentence with an independent clause and no dependent clause.
Thus, the correct answer is the first sentence.