At the railway station he waved goodbye to his friend until the train was .A. out of sight

问题补充：

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. 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。