他们是不是一直在背着我议论我？

Have they been saying things about me ___behind ___my ___back?

她的姐妹们开始背着她为派对制定计划。

Her sisters started making plans for the party ___behind ___her ___back.

他背着他的同事，自己申请了那个晋升机会。

He went ___behind ___his ___back and applied for the promotion himself.