So far, several cases of a disease, as bird flu, are reported to have been found in the country.
A. knowing
B. to be known
C. having known
D. known
网友回答
A. knowing
B. to be known
C. having known
(答案→)D. known
解析：考查非谓语。know 与cases为动宾关系所以用过去分词作定语。到目前为止据知是禽流感的几个病例在这个国家被发现并报道。