Here's why:
* Closed compound words are two or more words combined to create a single word, often written without spaces or hyphens.
* "Shoelace" is formed by combining "shoe" and "lace", and it is written as one word.
The other words in the sentence are not closed compound words:
* "final" is a single word.
* "undone" is a single word.
* "shoe" is a single word (even though it's part of the compound "shoelace").