I'd probably argue (C) is wrong, as I would have written, "an actor from the daily soaps," but that's not directly related to your question.
The use of "the illusion that ..." is perfectly idiomatic here. The writer is talking about a specific illusion, clearly defined — a common semantic technique native speakers use to focus on one particular variety of some general concept, even if that concept has not been previously mentioned. Examples:
When looking at the way business is run today, as compared with a century ago, we can see a much greater focus on ...
Early on Micheal revealed the ability to throw a ball harder and farther than any of his classmates.
I feel the need — the need for speed!
Side note: In this sentence, I feel "illusion" is inapt. I would have used either the stronger "delusion", or something else like "misconception", "misunderstanding", "mistaken belief", "false impression", or various other more appropriate words and phrases. Someone with a wide English vocabulary wouldn't feel the need to shoehorn "illusion" into where it doesn't fit.