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
网友回答
(答案→)A. out of sight
B. out of reach
C. out of order
D. out of place
解析：
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。