Correct answer:
c. Los maestros están ocupados
In this sentence, we have four words. First, los is the definite article that stands for the masculine plural form and means the. Second, maestros is a masculine plural noun and means teachers. Third, están is the conjugation of the verb estar for the third person plural in the simple present. Finally, ocupados is an adjective that translates into busy. So:
The teachers are busy means los maestros están ocupados