第11题: [单项选择]Some linguists believe that the______age for children learning a foreign language is 5 to 8. A. optimistic B. optional C. optimal D. oppressed 参考答案:C 答案解析:[解析] optimal“最佳的”符合句意。optimistic“乐观的”,optional“可选择的,随意的”,oppressed“受压迫的”都与句意不符,因此正确答案为C。