Correct option is B
Now, let's evaluate the given options:
(a) Song : Music → A song is a type of music, but music is not composed of songs in the same way a book is composed of words. (Incorrect)
(b) Leaf : Tree → Just like a book is made up of words, a tree is made up of leaves. (Correct)
(c) Sweet : Sugar → Sweet is a quality of sugar, but sugar is not composed of sweets. (Incorrect)
(d) Sleep : Bed → A bed is where you sleep, but sleep is not a part of a bed. (Incorrect)