In these sentences, you have to indicate the correct direct object according to the pronoun. The direct object indicates the object or person in which the action falls. The direct objects are:
Pronoun Direct Object
yo me
tu te
el/ella lo/la
nosotros nos
ellos/ellas los/las
So, for example, in the first sentence, los primos refers to the pronoun they, ellos in spanish, and to men, and according to that, the direct object is los.
Chica is feminine... reservada is feminine... so which of your options are feminine? Ella and la. Ella means she so it can't work, as that would mean she girl is very reserved. La is the femenine the. So that is your answer.
