题目

--- Robert is indeed a wise man. --- Oh, yes．How often I have regretted _____ his advice! A．to take           B．taking          C．not to take           D．not taking 答案：D已知命题“?x∈R，x2+2ax+1＜0”是真命题，则实数a的取值范围是A.（-∞，-1）B.（1，+∞）C.（-∞，-1）∪（1，+∞）D.（-1，1）