题目

Your house is always so tidy - how do you_______ it with three children?     A. manage          B. produce          C. train               D. plan 答案：A 设f(x)＝x2＋bx＋c(x∈R)，且满足，对任意正数a，下面不等式恒成立的是 [　　] A． B． C． D．