题目

He five years old two years ago.A. is B. was C. were 答案：【答案】B【解析】根据时间two years ago 两天前句子用一般过去时, 句子主语是第三人称单数, 谓语动词用was. 故答案为: B.3．已知二次函数f（x）=ax2+bx+c的图象开口向下，且顶点在第一象限，则它的导函数y=f′（x）的大致图象是（　　）A．B．C．D．