provided that 和 on condition that有什么区别?解释OK有追加分!

这两个都表示"如果",区别在哪?

I'm sorry you have decided not to go with us on the river trip, but ____ you change your mind, there will still be enough room on the boat for you.
A. even B. provided that C. nevertheless D. on condition that
这题选B还是D?为什么?
答案是B...
已经知道为什么勒....字典里查到勒...
谢谢

providing (that),provided (that)和on condition (that)的用法 provided that 和 on condition that有什么区别?解释OK有追加分! 请问given that与provided that是什么意思啊？谢谢 provided 和 unless 的区别 provided是什么意思？ provided that we can get a baby-sister,we will go to the theatre with you tonight.是什么意思？ how can i write a program that will output all of the factorials up to maximum number provided so that 和such that 翻译we'll be only too glad to attend your party provided that we can get a baby-sister.谢谢 so...that和such...that的区别