on the line：冒极大的险；以某种方式；冒风险。还可以理解为模棱两可；战斗准备状态等意思。
 
【例句】
She's on the line from her home in Boston.
她是在波士顿家中打电话。

He wouldn't put his career on the line to help a friend.
他不会为了帮助朋友而让自己的事业受到威胁。