题目

________she has got!A. What good knowledge of English            B. What good a knowledge of English C. How good knowledge of English             D. How good a knowledge of English 答案：D5．已知函数f（x）=|x-a|+m|x+a|（0＜m＜1，m，a∈R），若对于任意的实数x不等式f（x）≥2恒成立时，实数a的取值范围是{a|a≤-5或a≥5}，则所有满足条件的m的组成的集合是{$\frac{1}{5}$}．