by the loss of such a valuable jewel,Rachel’s mother hires the famous detective Sergeant Cuff to investigate the theft.
A. Troubling
B. To trouble
C. To troubled
D. Troubled
网友回答
A. Troubling
B. To trouble
C. To troubled
(答案→)D. Troubled
解析：troubled为过去分词短语作状语，它的逻辑主语是Rachel’s mother。