分析其句子成分?
问题描述：
分析其句子成分?
Until now scientists had very little clear evidence about the drug's role in preventing more serious effects of infection.
“about drug's role”是不是介词短语作补语?“in preventing more serious effects of infection”是什么?
effect在这里是什么意思？
答
至到最近,科学家对于这种药物在阻止感染的严重后果（方面）的作用只掌握很少的明确证据.主语 scientists谓语 had 宾语 very little clear evidence about the drug's role 宾语补足语 in preventing more serious ef...