1.social media 社交网络

例句:We have all witnessed the power of social media.
我们见证了社交媒体的实力。

2.back down 放弃；让步

例句:He had to back down on plans to backdate the tax changes.
他不得不放弃追溯税收调整的计划。

3.ruled out 排除

例句:The possibility of suicide was ruled out.
自杀的可能性已被排除。

4.tax rate 税率

例句:For low-paid workers, the marginal tax rate is at least 75%.
对于低收入的工人来说，边际税率至少为75%。