----I wonder how much for your services.--The first two are freethe third one costs $30

问题补充：

----I wonder how much for your services.

----The first two are freethe third one costs $30.

A. while

B. until

C. when

D. before

答案：

(答案→)A. while

B. until

C. when

D. before

解析：

这里考查while做连词，表示“然而”，表示两句话的对比关系，句意是：我想知道你的服务多少钱？---前两个是免费的，而第三个是30美元。选A。