Final answer:
The sentence 'Es mi tercer año en la universidad' is grammatically correct.
Step-by-step explanation:
The sentence is grammatically correct.
In Spanish, possessive pronouns like 'mi' (my) agree in gender and number with the noun they modify. Since 'año' (year) is masculine and singular, the correct possessive pronoun is 'mi'.
Therefore, the sentence 'Es mi tercer año en la universidad' is grammatically correct.
Learn more about Spanish grammar