The correct answer is B. Compound sentence
Step-by-step explanation:
The sentence presented is the integration of two complete sentences or independent clauses; the first one is "Many cars in the parking lot were double-parked" and the second one is "there wasn't enough room for additional cars". This is because each of these sentences includes a subject, verb and it expresses a complete idea. In this context, this sentence is a compound sentence (a sentence that integrates complete clauses) rather than a simple sentence.