A、  B、  C、  A助动词Do引导的一般疑问句，通常情况下用yes或no回答，而且Yes之后的内容与Yes的逻辑一致，(A)“是的，我们提供多种经济舱票价”是正确的回答。

Is check ok?
(A) Yes, the condition of this machine is very good.
(B) Yes, we should check if everything is Ok.
(C) Yes, you can use it.

Do you have special airfare to New York, the economy class?
(A) Yes, we offer a wide range of economy airfares.
(B) No, every student in the class is fair.
(C) Yes, we don’t have economy airfare to New York.