"لكن لا يمكن للمرء أن يعرف ذلك أبداً."
الترجمة:But one would never know it.
I think only 3 is correct because the sentence says: ذلك it is not giving the meaning of ذلك
could . That will become more flexibility , when we use could instead of "would"
I agree with you . I have some confuse from this sentences could . That will become more flexibility , when we use could instead of "would"
That is mean ذالك .you have mistake we can't say it for some thing to far away.
I think ( But,One would never know it ) not correct enough in this case , i think ( But. one could never know it ) this more corect than anther one because when " could"that it tells us about ablility.