题目

设函数在区间[a－1，a＋1]上单调递减，则实数a的取值范围是( ) A. [－∞，2)    B. (1，2]         C. (0，3]         D. (4，＋∞] 答案：BA new library is being built ______ there was a playground. [     ]A. that B. in whichC. whereD. when