Question

Toma __________ libros.

Answer 1

Toma __________ libros.

las

el

los

la

Answer 2

Los

Answer 3

Toma means he/she/it takes.

libros ends in an -os which the -o usually means it is masculine and the -s means its plural so you must have an article that is both masculine and plural

The masculine articles are el and los and the plural articles are los and las. Pretty straightforward really.

A common example to the rule of ending in -o to mean masculine would be "la moto" for motorcycle but that's just because it's short for "la motocicleta".