The correct answer is (Smith 122). According to MLA Handbook (8th ed.), a parenthetical reference for a book with one known author should include the author’s last name and the page number(s) of the quotation, paraphrase, or summary you are citing; there should be no punctuation between the author’s last name and the page number. In this case, the author of the book is Smith, and the quotation was taken from page 122 of Smith’s book; consequently, the parenthetical reference should be (Smith 122).