If a passenger wants to change their ticket class from economy to business， you should：

If a passenger wants to change their ticket class from economy to business， you should：
A.Sure， it's free.
B.There will be an upgrade fee. Let me check the availability and the amount for you.
C.Business class is always full.
D.You can't upgrade your ticket.
正确答案：B
试题解析：当乘客想从经济舱升舱到商务舱时，通常会有升舱费用。客服应先检查商务舱的座位可用性，然后告知乘客升舱费用的具体金额。