What do you do when a passenger wants to upgrade their seat class during check - in？

What do you do when a passenger wants to upgrade their seat class during check - in？
A.Upgrades are not available.
B.Check the availability of the upgrade and inform the passenger about the additional cost.
C.Upgrade them for free.
D.Charge a hidden fee for the upgrade.
正确答案：B
试题解析：当乘客在办理登机手续时想要升舱，工作人员应检查升舱的座位是否可用，并告知乘客升舱所需的额外费用。