29．---- 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
29．---- 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
A
考查连词的用法。这里起转折作用,while表示”但是”,可接句子.”前两个免费,但第三个要收费30元”