of cours 和certainly用法上有什么不同啊?

certainly的用法例句
无疑地，肯定地；不可否认地
必定，一定，有把握地
[用于回答]行；当然；没问题

certainly的用法例句
Icertainlywould, thanks.
我当然愿意，谢谢。
Certainly. What do you want to buy ?
当然可以，您要买些什么水果？
Clerk:Certainly, sir. How much do you draw?
职员：当然可以，先生。您要取多少钱？