The correct answer is B. Complex
Step-by-step explanation:
The sentence "Running out of time, we arrived at the flower shop five minutes before closing" contains two clauses one independent clause with a complete idea and a subject and verb "we arrived at the flower shop five minutes before closing" and one adverbial clause that is dependent "Running out of time" because it does not contain a subject or express a complete idea. In grammar, sentences that contain an independent clause and a dependent one are considered as complex sentences, thus, the sentence presented can be classified as complex.