题目

______ English is more and more important for our future, we should spend more time on it.          A. Since    B. While   C. In case          D. Even though 答案：A 画出下列函数的简图： (1)y＝3＋sinx，x∈[0，2π]； (2)y＝2－sinx，x∈[0，2π]； (3)y＝－cosx＋3，x∈[－π，π]．