stifle的现在分词是哪个

例句：

The government failed to stifle the unrest.

政府没有制止住动乱。

They hope the new rules will not stifle creativity.

他们希望新规则不会压制创意。

These measures will have the effect of stifling competition.

这些措施会产生扼杀竞争的后果。