Answer:
Your answer would be that the the sentences that are punctuated correctly are the last three.
Explanation:
a) Gabriel will travel to Peru (where his mother was born) next month
b) Bears in Space- which is my favorite movie- is on at eight o'clock tonight.
c) Charlie, my oldest cousin, just got a job at the car wash
Sentence A contains a parenthetical comment. Parentheses are used to enclose incidental or supplemental information. In this case, the parenthetical information specifies that Peru is Gabriel's mother birthplace. That is why the sentence is correct.
Sentence B contains an em dash. The em dash can take the place of commas, parentheses, or colons. In this case, the em dash has been used as a pair of a commas since it is separting a nonessential relative clause from the main clause. On the contrary, "apples which come (...)" is not correct because the information by the relative clause is nonessential, so it should be between commas. Then, "the friend -whom I(...)" is also wrong because of the relative pronoun. <em>Whom </em>should be used as an object.
Sentence C contains an appositive phrase. An appositive is a noun or noun phrase that renames another noun right beside it. In this case, <em>my oldest cousin,</em> renames the noun <em>Charlie.</em> As the information provided by the appostive is not essential to complete the meaning of the sentence, it is offset wtih commas. It can be removed and the meaning of the sentence would be left unchanged.