Read the sentence. The flag of the United States, which is often called the Stars and Stripes, originated during the Revolutionary War. Which statement about the underlined phrase is true? The phrase

Read the sentence. The flag of the United States, which is often called the Stars and Stripes, originated during the Revolutionary War. Which statement about the underlined phrase is true? The phrase is a relative pronoun. The phrase is an essential adjective clause. The phrase is a nonessential adjective clause. The phrase is connected to the sentence with a relative adverb.