So far several cases of a disease as bird flu are reported to have been found in the co

问题补充：

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

答案：

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。