is certain is prevention is more important than treatment .
A. It;that
B. What;that
C. As;what
D. What;what
网友回答
A. It;that
(答案→)B. What;that
C. As;what
D. What;what
解析：“ is certain”在句中做主语,主语从句缺少一个主语,需要用What; “ prevention is more important than treatment .”系表语从句,句意与结构完整,只有that,可以这样用