下面句中有一处错误，请找出来并改正。
Sandy come from Beijing, but he lives in Donghai now.
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如果+0.5米表示水位上涨0.5米，则水位下降0.3米可表示为____ 米．
Look at the two pens．The red one is____ (you)and the green one is____ (I)．
