Answer:
Los niños _SE LAVAN_ las manos
Explanation:
Los niños _SE LAVAN_ las manos
("The kids wash their hands")
When you conjugate a reflexive verb (like 'lavarse'), you have to use the pronoun in front of the verb. So, indicative present of lavarse is:
Yo me lavo ...las manos
Tu te lavas ...las manos
Él se lava ...las manos
Nosotros nos lavamos ...las manos
Vosotros os laváis ...las manos
Ellos se lavan ...las manos
That way, it indicates the action is done on the person itself, not on others ('Yo lavo las manos' - I wash the hands - could be performed with anyone's hands).
