Many Thanks

1.  I exchanged them multiple times, could not figure out

2. yes, that sound better.  I try to use "which" to refer the first two scentences, but can not make it work :(

3. good catch,  I can not distinguish these two. I will check on dict.cn.

4. I realized that when I heard the original one.

5. thanks.  I can not make the spelling check in my word work :(

Thanks again.