题目

二次函数y=ax2+bx+c的图象如图所示,下列结论:①a+b+c>0;②a-b+c<0; ③abc<0;④2a+b<0.其中正确结论的个数是(   )     A.1     B.2     C.3     D.4   答案：A — Has Mr. Tom White arrived? — Yes, already. _____ he wait outside or just come in?                 A. Shall          B. May  C. Could D. Must