Final answer:
The correct substitution for 'ihre' would be 'ihren', which is the accusative form of 'ihre'.
Step-by-step explanation:
Substitute a pronoun for the highlighted word in the sentence below:
Katrina spielt Musik. Nach dem Konzert, kaufen ihre Eltern Katrina immer das Abendessen.
The highlighted word in the sentence is 'ihre' which is a possessive pronoun. In German, 'ihre' is used to refer to 'their' in English. Therefore, the correct substitution for 'ihre' would be 'ihren', which is the accusative form of 'ihre'.
Learn more about pronoun substitution in German