The 16 male child had to have certain qualities. 17 was the ability to identify the belongings of his predecessor, or rather his previous self.
答案：(A) chosen
前一句提到達賴喇嘛圓寂後便展開尋訪轉世靈童的行動，故此處指「被選中的」男孩，用過去分詞 chosen 當形容詞；searching 是主動（孩子並非在尋找），dead（死去的）與 previous（先前的）都與文意不合。
讀懂前一句的人幾乎都對。
choose-chose-chosen 你一定背過，但大概沒把 chosen 當成一個形容詞記住：「被選中的」。the chosen one 就是「天選之人」。
作答線索在前一句 Whenever a Dalai Lama died, a search began for his reincarnation.（每當達賴喇嘛圓寂，尋訪轉世靈童的行動就展開）。既然有「尋訪」，接下來提到的這名男孩自然是「被選中的」那一位——本句自己完全沒有交代挑選的動作，不回頭看前一句就選不出來。分詞當形容詞，要看該動詞與被修飾名詞之間的關係：主動用現在分詞，被動用過去分詞。the boy searching for his dog（正在找狗的男孩）是主動，the boy chosen for the role（被選來擔任這個角色的男孩）是被動。這名男孩是被找到、被選中的一方，所以用 chosen。
the chosen one（天選之人）、the chosen few（少數獲選者）、be chosen as／for（被選為／被選中做…）。
Whenever a Dalai Lama died, a search began for his reincarnation. The 16 male child had to have certain qualities. 17 was the ability to identify the belongings of his predecessor, or rather his previous self. Another requirement was 18 he should have large ears, upward-slanting eyes and eyebrows. Besides, one of his hands should bear a mark like a conch-shell. The successful candidate, usually 19 two or three, was then removed from his family to Lhasa to begin spiritual training for his future role. The Panchen Lamas were chosen in a similar way.
The reincarnated leaders were always "discovered" in the households of lowly families 20 noble ones. This was to ensure that no single and powerful noble family could seize the title and pass it to the next generation.