C的逻辑不对吧:Researchers agreed that ...., but they agree that.... (B)Researchers agreed that (study... but more research....)更符合逻辑意思 而且比较对象是balloon angioplasty 和the balloon procedure 助动词要补充才好 for doing和to do: for doing前一定有名词,而to do前不需要一定有名词 we need more research for determining... 被动语态: more research was needed for determining we need to determine whether.......with more research 被动语态: more research was needed to determine |