Final answer:
The correct Spanish conjugation of 'seem' for 'Los niños' is 'parecen'.
Step-by-step explanation:
The correct Spanish conjugation of 'seem' for the subject 'Los niños' is 'parecen'. The verb 'parecer' is used to express the verb 'seem' in Spanish. So, the correct sentence would be 'Los niños parecen muy felices.'
Learn more about Spanish verb conjugation