He’ll never forget his stay in the park he found his cellphone which had gone missing day

问题补充：

He’ll never forget his stay in the park he found his cellphone which had gone missing days before.

A. that

B. when

C. where

D. which

答案：

A. that

(答案→)B. when

C. where

D. which

解析：考查定语从句：句意：他永远忘不了在公园逗留的期间，那时他发现了几天前丢失的手机。先行词是his stay，表示时间，定语从句中缺少时间状语，选B。