单项选择题

Questions 14 to 17 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions. Now listen to the passage. Codes are scanned by ______.

A．the checkout clerk
B．the customers themselves.
C．a laser beam of light.
D．the cash register.

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单项选择题

单项选择题

Questions 14 to 17 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions. Now listen to the passage. Codes are scanned by ______. 您的浏览器不支持 audio 元素。