翻譯：她將永難忘記她在那兒的停留,（因為）在那次停留期間她找到了兩年前失蹤的兒子.
此題考查定語從句的關(guān)系詞的選擇.
1.先行詞是her stay,而不是there,因為定語從句所修飾的先行詞只能是代詞/名詞（短語）,而不能是副詞.
此題中的stay是一個名詞,意思也是“停留/逗留”.
2.將先行詞her stay放入定語從句中,連接為：
(when) she found her son who had gone missing two years before
= (in/during which) she found her son who had gone missing two years before
= (in/during her stay) she found her son who had gone missing two years before
在她（在那兒的）逗留期間,她找到了兩年前失蹤的兒子.
很明顯,該定語從句缺少時間狀語.
即所謂的關(guān)系副詞when = 介詞(in/during) + 關(guān)系代詞which = 介詞(in/during) + 先行詞(her stay).
3.而關(guān)系代詞that/which只能等于先行詞her stay,無法直接放入定語從句中做成分；
where在定語從句中充當?shù)攸c狀語,而不是時間狀語.