一、选择题(本大题共12小题,每小题5分,共60分.在每小题给出的四个选项中,只有一项是符合要求的) 1.若a,b为实数,则ab0是az护的() (A)充分不必要条件.(B)必要不充分条件. (C)充要条件.(D)既不充分也不必要条件. 2.若x0,一l了0,则下列不等式成立的是() (A)叮冰叮2.(B)扩 First, the multiple-choice questions (the title of a total of 12 small questions, each question 5 points, a total of 60 points. In each question given four options, only one is in line with the requirements) 1. If a, b is For real numbers, then ab0 is guarded by az () (A) sufficient unnecessary conditions. (B) necessary insufficient conditions. (C) necessary and sufficient conditions. (D) is neither sufficient nor unnecessary. 2. if x0, a If l is 0, then the following inequality holds: () (A) 叮 叮 叮 . . . . . . . (B)