问题
选择题
At the railway station，he waved goodbye to his friend until the train was ________.
A．out of sight
B．out of reach
C．out of order
D．out of place
答案
答案：A
句意为：在火车站，他挥手同他的朋友告别直到火车看不见了。out of sight看不见，符合题意。
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