Final answer:
The definite articles for each noun are: el libro, la mesa, los relojes, las computadoras.
Step-by-step explanation:
The definite article 'el' is used with the singular masculine noun 'libro', e.g. 'el libro' (the book).
The definite article 'la' is used with the singular feminine noun 'mesa', e.g. 'la mesa' (the table).
The definite article 'los' is used with the plural masculine noun 'relojes', e.g. 'los relojes' (the watches).
The definite article 'las' is used with the plural feminine noun 'computadoras', e.g. 'las computadoras' (the computers).
Learn more about Definite articles in Spanish