— I wonder how much you charge for your services．
— The first two are free the third costs $30．
A. while
B. until
C. when
D. before
网友回答
A. while
B. until
C. when
D. before
解析：考查连词：A. while然而，虽然，当…时候B. until直到C. when当…时候D. before在…前面，句意：--我想知道你的服务要多少钱？--前两个是免费的，第三个是30美元。选A。