The answer is none of the above because A, B and C refer to either a comparative or superlative form and the sentence above is not comparing anything. It is only a statement about Sonja's interest in music.
The comparative form is used to compare one noun to another, let alone the superlative which is used to compare three or more nouns.
When you understand the problem completely, you can build the project up from it. defining the problem is like defining a word in some text; when you know it, you know the rest of the content.
