The difference with (C) is slightly different. (C) is wrong because the conclusion doesn't concern a broader range of phenomena. The conclusion tells us that playing a musical instrument alters brain structure; the evidence also concerns playing a musical instrument in general, and so there's no narrowing of the phenomena. The stimulus does specifically mention the piano, but only to describe a certain area of the brain that distinguishes the different sounds of the piano, as opposed to playing the piano resulting in a larger brain. Hope this helps!