单项选择题
Passage One Questions 27 to 30 are based on the conversation you have just heard.
A．Collect money and help new users. B．Maintain the automated system. C．Stay alert to any emergency. D．Walk around and guard against car theft.
A．It worried publicly. B．It felt much relieved. C．It made no comment. D．It welcomed the decision.
A．It takes time for the human body to get used to it. B．It lacks the vitamins and minerals essential for health. C．It enhances immunity to certain diseases. D．It helps people to live a much longer life.