Final answer:
The appropriate personal pronoun to fill in the blank is 'les' and it indicates the importance of the students' studies.
Step-by-step explanation:
The appropriate personal pronoun to fill in the blank in the sentence 'A los estudiantes. Importan sus estudios.' is les.
'Les' is the plural indirect object pronoun in Spanish, used to refer to 'the students' as the recipients of the action. In this case, it indicates that their studies are important.
Example: A los estudiantes les importan sus estudios para su futuro.
Learn more about Personal pronouns in Spanish