stifle的現在分詞是哪個

　　例句：

　　The government failed to stifle the unrest.

　　政府沒有制止住動亂。

　　They hope the new rules will not stifle creativity.

　　他們希望新規則不會壓制創意。

　　These measures will have the effect of stifling competition.

　　這些措施會產生扼殺競爭的后果。