他背弃了家族生意，转而投身音乐。

He ___turned ___his ___back ___on the family business and pursued music instead.

当他们最需要帮助时，最老的朋友却抛弃了他们，这让他们感到被背叛了。

They felt betrayed when their oldest friend ___turned ___his ___back ___on them in their time of need.

这位候选人在选举后背弃了他的竞选承诺。

The candidate ___turned ___his ___back ___on his campaign promises after the election.