The correct answer would be the last one. I took the quiz and I can confirm that "I would take my brother to the park" is the correct answer.
The sentence that contains a restrictive clause is A. They decided to meet where the band was performing.
A restrictive clause is also known as an essential clause, because its existence is important for the meaning of the sentence. Because of that, it is not set off by commas.
The answer is .................................,.,,..,,.. a
Since there is no underlined portion we aren’t able to answer the question. Sorry