同学你好，该知识点来自沪江网校《英语零基础直达大学四级【抢学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好：
这里选4。
根据课文最后两段可以推测，只有4 knew that the writer could pay her bill 符合课文的含义，这正是课文所暗示老板当时的心态，而其他3个选择都与课文内容不符。
参考---
1 was angry because the wirter couldn't pay her bill，很生气，因为作者不能买单；
2 was sorry that the writer couldn't pay her bill，为作者不能买单感到抱歉；
3 knew that the writer couldn't pay her bill，知道作者不能买单；
4 knew that the writer couldn pay her bill，知道作者可以买单。

祝学习愉快！