I think the question is trying to emphasize that, out of convention, most native speakers would say either "near the salon" or "next to the salon", and likely not "near to the salon," and certainly not "next the salon."
The problem many test writers seem to overlook is that a question like this can really trip up a learner, because the natural follow-up questions that arise are: "Wait? Couldn't we use either one? Is near to incorrect for some reason?"
The answer to that is more complicated than most exam books want to delve into. There are times when "near to" is idiomatic, and I probably wouldn't go so far as to say it's "incorrect" in a context like, "Mary's house is near to the salon."
But getting back to the main thrust of the question, even if I wouldn't deem it "incorrect," I certainly think "Mary's house is next to the salon" is a marked improvement, so I don't have too much of a beef with the point the test question is presumably trying to emphasize.