So during the second second, the velocity is not changing.
因此在第二秒内，速度没变。
Let's now go to the second second and let's see what happens there.
现在来看第2秒，看看发生了什么。
Second, second-hand equipment imported common problems?
二手设备进口中常见的问题？
Three classes are available on the high speed trains: business, first and second. Second class is equivalent to but far more comfortable than economy class on a airplane.
高铁列车座位分三等：商务、一等和二等。二等座相当于飞机上的经济舱，不过舒服多啦。
Three classes are available on the high speed trains: business, first and second. Second class is equivalent to but far more comfortable than economy class on a airplane.
高铁列车座位分三等：商务、一等和二等。二等座相当于飞机上的经济舱，不过舒服多啦。
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