Mi mamá los calcetines azules por los calcetines blancos. (2 points) cambio cambia cambian cambiamos

cambia

Explanation:

You need to use the conjugation of the verb cambiar with the personal pronoun of ella (mi mamá)

Here is the translation to the complete sentence:

My mom changes the blue socks for the white socks.

Here is the indicative conjugation of the verb CAMBIAR in present:

Presente

yo cambio

tú cambias

él/ella/Ud. cambia

nosotros cambiamos

vosotros cambiáis

ellos/ellas/Uds. cambian

As you can see the options are conjugated with different personal pronouns cambio for yo, cambian for ellos and cambiamos for nosotros.

answer: the answer is b. se quejan because it's in the plural form.