No one has been able to trace the author of the poem.A. stillB. yetC. alreadyD. just

问题补充：

No one has been able to trace the author of the poem.

A. still

B. yet

C. already

D. just

答案：

A. still

(答案→)B. yet

C. already

D. just

解析：yet 常用于现在完成时的否定句中, 意为“尚, 还”。