The apartment complex consisted of individual buildings , with apartments which were accessed from inside a common entry way . I pulled my bike in , placed it by the door , and went into the apartment to make a phone call . When I returned ( less than a few minutes later ) , the bike was gone .

Question: Why was the bike stolen ?
Answer: The narrator left it on the grass .The thief knew the lock combination .It was left unlocked by the narrator .None of the above choices .