Final answer:
In the given sentence, 'who enjoys many different subjects' is the nonrestrictive modifier. It provides additional information about Marlena but is not essential for the sentence's main message.
Step-by-step explanation:
In the sentence: 'Marlena, who enjoys many different subjects, likes history and geography the best', the nonrestrictive modifier is 'who enjoys many different subjects'. This clause gives us extra information about Marlena but is not essential to the meaning of the sentence. The sentence would still make sense if it was removed. Nonrestrictive modifiers, also known as nonessential clauses, are usually set off by commas in a sentence, which is the case here. They add more information to a sentence but are not crucial to understanding the core message.
Learn more about Nonrestrictive Modifier