Returning to the room, .
A. the book was lost
B. I found the book missing
C. the book was missing
D. I found the losing book
网友回答
A. the book was lost
(答案→)B. I found the book missing
C. the book was missing
D. I found the losing book
解析：现在分词是主语的动作，因此I做句子的主语；missing表示“丢失”。