Yes, but there is normally "the" before USA and UK.
Of the top ten Labrador Retrievers, eight of them were black.
Student or Learner
I have some idea about using the term "out of", for example; "I got 6 marks out of 10", "out of five countries, USA and UK are the most industrial countries" etc.
But I am quite weak at using the term "of something". "Of the five countries, USA and UK are the most industrial countries" is this right?
'Of something' is usually pretty easy. Try arranging the sentence in a more normal way, then transform it like this:
"Julia was the tallest of the five girls." -> "Of the five girls, Julia was the tallest."
"The US and the UK are the most industrial of the five countries." -> "Of the five countries, the US and the UK are the most industrial." You don't need to add "countries" again - in fact, you shouldn't.
I can't promise that this will work for all sentences, but it might give you an idea of how to use it.