So far several cases of a disease as H1N1 are reported to have been found in the countr

问题补充：

So far, several cases of a disease, as H1N1, 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

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