单选题 We cannot process your order ______ we have received the deposit mentioned in our mutually agreed contract.
A. while
B. during
C. until
D. if

【正确答案】 C

【答案解析】中级问题空格内应填入连词，此时需要通过分析词语来选择答案。umtil既可以做介词，又可以做连词。句意是必须在收到订金之后才能进行处理，所以最恰当的选项是until。
[高频词语] process an order 处理一个单 mentioned 提到的 mutually agreed 达成共识的