use of "of which"

[lovelymimi_04]

Which of these sentences are correct? (not the best answer)
1. That's the country of which the birthrates need to be controlled.
2. That's the country of which birthrates need to be controlled.
3. That's the country the birthrates of which need to be controlled.

Thanks

[Horsa]

I don't like any of them since the formality inherent in 'of which' seems out of place but the third is the only option that works.

[Naamplao]

Originally Posted by Horsa

I don't like any of them since the formality inherent in 'of which' seems out of place but the third is the only option that works.

I don't like any of those answers at all...not even #3.

[lovelymimi_04]

that means the #1 and #2 are not grammatical?

[Horsa]

As I said I don't like any of them. But at least in number 3 'of which', which here can only mean 'of the country in question', is attached to birthrate and so conveys some meaning. I can't imagine any of them including number 3 being uttered by a native speaker.

[lovelymimi_04]

Thanks. I know that people say:
"That's the country whose birthrates need to be controlled."
They don't use "of which..." actually. It seems to grate. But I wonder how we use it (grammatically) as it was mentioned in the exercise book.