I'm sorry to have you waiting so long for Marcia ,and I’m af

I'm sorry to have you waiting so long for Marcia ,and I’m afraid it'll be ten minutes ()```````
I'm sorry to have you waiting so long for Marcia ,and I’m afraid it'll be ten minutes ()she comes back.A.before B after C until D when
我的练习书上选B,可我觉得选A,意思不就是在她回来前还有十分钟吗?很纠结,请高手知道,
真的很苦恼，主要是区分after 与before在句中的意思，用法和区别。