The correct answer is B. Service industries have begun to play an important role in Philadelphia, and the city’s economy is more complex.
Explanation;
In grammar, faulty coordination occurs when two ideas, concepts or elements that do not have the same importance or do not belong to the same topic are connected by using the coordinating conjunctions and, but, or that should only be used when ideas belong to the same topic and have the same importance. Additionally, this type of error leads to constructions or sentences that are confusing or sound awkward.
Considering this, the sentence that is an example of faulty coordination is "Service industries have begun to play an important role in Philadelphia, and the city’s economy is more complex" because in this sentence the first idea related to the role of service industries in Philadelphia do not belong to the same level of importance that the second idea that states the city economy is more complex. Indeed, the second idea is the consequence of the first and should be linked by using subordinating conjunction like as a result, therefore, etc but never the coordinating conjunction "and".
