The relationship between "Statue" and "Size" is that a statue can vary in size. Similarly, the relationship between "Song" and the missing word should involve something that can vary or be associated with a song. So, the missing word should be related to the characteristics or attributes of a song. The correct answer is: Tune. A song can vary in its tune, just as a statue can vary in its size.

We are looking for a word that represents a characteristic or attribute of a song, something that can vary or be associated with songs.

Option 1: Words - This doesn't fit the analogy because "Words" are a part of a song but do not represent a characteristic that varies or can be associated with a song as a whole.

Option 2: Beauty - While beauty can be associated with songs, it doesn't directly represent a characteristic or attribute that varies within a song.

Option 3: Tune - This is the correct answer. The "Tune" of a song is a key characteristic that can vary between different songs. Just as statues can vary in size, songs can vary in tune.

Option 4: Singer - This doesn't fit the analogy because "Singer" is a separate entity related to a song but doesn't represent an inherent characteristic of the song itself.