Relative clause

[hector51]

Hi!
This is a sentence from my test:(find the sentence which has the same meaning as the original sentence)
Rod Lee has won an Oscar.I know his sister.
a.Rod Lee,of which sister I know,has won an Oscar.
b.Rod Lee,whose sister I know,has won an Oscar.

yeah,the correct answer is "b",I know this is a sentence contains non-restrictive relative clause,can I use "of which" instead of "whose" here?my teacher said I can't,but can you explain to me why not? Thanks for helping!!!

[MrPedantic]

Hello Hector

No, you can't use "which", because Rod is a person.

You can also use "of whom"; but it sounds very formal and stilted (i.e. I don't recommend that you use it):

3. Rod Lee, the sister of whom I know, has won an Oscar.

MrP

[hector51]

Thanks for your clear reply,MrPedantic,now I now where my mistake is ,really appriciate your help !!!

[MrPedantic]

It's my pleasure – have a cheery Friday,

MrP