1.backbone 主干；主心骨；支柱

例句：As a group, they are meant to be the backbone of the market economy.
作为一个团体，中产阶级意味着市场经济的支柱。

2.when it comes to 当谈到；涉及到

例句：Yet the majority of these employees have no voice, especially when it comes to their own safety.
然而，这些雇佣员工大多数没有发言权，尤其是涉及到自己的安全问题。
3.regardless of 无论；不管

例句：Every problem you have is your responsibility, regardless of who caused it.
不管是谁造成的，你都需要对你面对的每个问题负全责。

4.a total of 总计；总共；总数为

例句：The couple eventually took a road trip across the states killing a total of 11 people.
最终，这对同伙在穿越全美的公路旅行中一共杀害了11个人。