题目

He _______ us that everything would go according to plan, but it turned out a failure. A. suggested        B. demanded        C. ordered        D. guaranteed 答案：D一束光线从空气中射入水中时，速度将______（选填“变大”、“变小”或“不变”），传播方向将______（填“一定改变”或“可能不变”）