I think "It" should be acceptable as well. That is, "It is a very nice carpet."
I don't think so.
Which carpet is nice?
Which one, this one here or that one over there?
Is weird in English too, isn't?
It, this and that are interchangeable in English but alter the meaning. If i am not wrong Hungarian uses for it just nothing and ez and az replace the void with this or that.
I would say sometimes there is a need in Hungarian for what is "it" in English. And, for lack of an "it", they use "ez" or "az", the latter being the more frequent choice. But you are right, sometimes it is just nothing or, better yet, a totally different construction.
Nothing. It should be accepted.
As I understand, "rug" is a piece of floor covering, that you place in front of the couch, under the coffee table, next to the bed, etc. - This is "szőnyeg" in Hungarian.
And "carpet" is more frequently used for the wall-to-wall covering that is attached to the floor of an entire room. - This is "padlószőnyeg" or "szőnyegpadló" (carpet+floor) in Hungarian.
I am not sure how strong these definitions are in English. And there may be regional differences I imagine. Anyway, both "rug" and "carpet" should be accepted.
If it covers the entire floor from wall to wall, I would be more inclined to call it "carpeting", especially if it's stuck/glued to the floor.
A carpet is a floor covering that may not extend right to the walls (though it could); and you'd buy it in one piece, rolled up. (Whereas carpeting could be made up of little squares or large rectangles stuck next to each other until the floor is covered.)
So for me at least, the main difference between a carpet and a rug is size: rugs are smaller.
You could, but it might stretch the definition of szép a little. Szép is more a description of physical beauty while 'lovely' has a connotation of being charming or kind, which is more behavioural. The most common translations of szép are 'beautiful', 'pretty', and 'nice'. (Which all are accepted throughout the course.)
The dictionary I use suggests as translations for 'lovely' the words aranyos (lit. golden), bájos (lit. charming), and kedves (lit. kind, nice).