Translation:This is the apple whose color is red.
I understand that there are grammatical reasons for the sentences of this section, but I wonder whether other more natural ones can illustrate the same grammatical points. Here, "Αυτό είναι ένα κόκκινο μήλο." conveys the same information as the original sentence. On the other hand, "Peter, whose father is an engineer, wants to study medicine." is a more natural sentence.
I definitely agree and I was about to post a similar comment. I am a native English speaker, and (in English at least) I would never say "This is the apple whose color is red." In English, the relative pronoun "whose" tends to only have human antecedents (or at the very least refer back to something animate). Instead, I would say "This is the apple that/which is red." I really like your example sentence where the pronoun "whose" fits much more naturally.
In Greek, though, του οποίου does not have to refer to human beings, it can refer to anything grammatically masculine or neuter.
Ο τουρισμός, του οποίου η συνεισφορά στο ΑΕΠ είναι σημαντική, αυξήθηκε τον τελευταίο χρόνο. (Tourism, whose contribution to the GDP is important, has increased in the last year).
Similarly, της οποίας can refer to anything feminine.
Η χώρα αυτή, της οποίας ο λαός υποφέρει... (This country, whose people is suffering...)
True about the use of του οποίου in Greek but translating it into English, as the exercise asks you to do, presents problems, since RaleighStarbuck is quite right, we only use whose for people, not things. In this example, the correct translation is more like 'this is the apple which is red in colour', which isn't accepted - it's not particularly elegant English but it is right, unlike 'whose colour is red'. In your examples (which are very useful, thanks!) the translations would therefore include the phrases 'the contribution of which to GDP is important' and 'the people of which are suffering' - though, to be honest, when translating I would look for an alternative way of expressing it, since these are pretty clunky clauses :-)
Just to reassure myself that what I remembered was accurate. I referred to some reliable grammar books which you'll find:
All of which show that "whose" is used with inanimate objects.
That doesn't mean that I don't find the sentence awkward and would prefer: "That is the apple that is red." But in these exercises it's always best to adhere to the sense of the source language.
Fair enough! Technically it can be used it seems, though it really isn't common in the UK to use it this way (possibly more so in the US, I don't know). Thanks for the links, and I'll be following your advice about the source language from now on! :-)
OK, here is the view of: https://en.oxforddictionaries.com/definition/whose. :-) Not common but correct even in UK.
Yes, this is not the most melodious sentence but it's trying to show the relative pronoun "του οποίου". This is better "Πέτρο, του οποίου ο πατέρας είναι ένας μηχανικός, θέλει να σπουδάσει ιατρική." I'll try to fit it in. Thank you.
"of which" = whose; and should be accepted, especially as "whose" suggests masculine/feminine in English.
Why is wrong "the color"? I wrote "this is the app;e whose the color is red" and don't accept