题目

已知二次函数的图象如图所示，有下列4个结论，其中正确的结论是 [ ]A.abc<0B.b>a+cC.2a-b=0D.b2-4ac<0 答案：B—Computer is so useful. It can do almost everything. —Yes, but it ______ what to do.A．will tellB．has knownC．must be toldD．is told