单选题 In the busy holiday season, extra buses are provided to ______ the existing service.
A. supplement B. complement C. implement D. experiment

【正确答案】 A
【答案解析】[解析] supplement“补充”；complement“补足，补助”；implement“实施，执行”；experiment“进行实验，尝试”。由题意可得正确答案为A。