The answer is
La revista Cosas es mi favorita. ___La compro_________ todos los meses.
The female and singular pronoun <u>La </u>is replacing the magazine (revista Cosas) which in Spanish is also female.
the other options do not apply because:
<u>Lo</u> compro is male gender
<u>Las</u> and <u>los</u> are for plural and the sentence states only one magazine.
Ellos caminan para su casa
The second one, ¿Cuándo es el partido?
Comida the answer is comida
Yo compro una regla para mi clase de matemáticas.
