题目

Unlike watching TV, reading is a highly active process _______ it requires attention as well as memory and imagination. A. until             B. but              C. unless             D. for 答案：D 解析: 检查考生对逻辑关联用语的掌握和运用能力。for引导的是并列分句。功能ⅰ）对前面的分句加以解释，ⅱ）说明推断的理由，for引导的句子只能后置。平方根是（    ）.