Customer 对象所采取的实际 操作仅仅是检查几个点上的模拟时间，并将持续时间记录到 waittime 和 checkouttime 监控程序中。

The only real actions taken by a Customer object are checking the simulated time at a couple of points, and logging some durations to the waittime and checkouttime monitors.

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研究人员跟踪调查了5000名高中学生，该调查一直持续直到他们步入中年，总计22年。研究人员每年会记录一次调查对象的体重和体质指数(BMI)。

The researchers followed 5, 000 high school seniors until middle age, tracking their body weight and body mass index (BMI) annually for 22 years.

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研究人员跟踪调查了5000名高中学生，该调查一直持续直到他们步入中年，总计22年。研究人员每年会记录一次调查对象的体重和体质指数(BMI)。

The researchers followed 5,000 high school seniors until middle age, tracking their body weight and body mass index (BMI) annually for 22 years.

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