So a pendulum one meter long has a period of about two seconds.
因此1米长的钟摆，所用周期是2秒。
The customer left his "private" meter in place for a portion of each billing period.
用户在每一个收费期的部分时间里换上他的“私人”电表。
The customer left his "private" meter in place for a portion of each billing period.
用户在每一个收费期的部分时间里换上他的“私人”电表。
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