Answer: The sentence that correctly uses an appositive phrase to combine the two sentences is "Margaret Mead, an American anthropologist, is widely known for her studies of primitive societies".
Explanation: An appositive phrase is a noun phrase that renames a noun or pronoun that is found immediately before or after this phrase. Moreover, an appositive phrase must always be separated from the rest of the elements in a sentence by means of commas. The only sentence that correctly uses an appositive phrase to combine the two sentences provided is "Margaret Mead, an American anthropologist, is widely known for her studies of primitive societies". In this sentence, "an American anthropologist" is the appositive phrase as it is a noun phrase that is renaming the proper noun "Margaret Mead", which comes immediately before the phrase. Furthermore, commas have been used to separate "an American anthropologist" from the rest of the sentence.