题目

The new CRH train between Beijing and Shanghai _______ speed can reach about 380km/h will benefit people a lot. A. whose               B. where                 C. that                      D. which 答案：A 解析: 略14．下列对应关系中是集合A到集合B的函数的个数是（　　）①A=R，B={x|x＞0}，f：x→y=|x|；②A=Z，B=Z，f：x→y=x2；③A=Z，B=Z，f：x→y=$\sqrt{x}$；④A=[-1，1]，B={0}．f：x→y=0；⑤A={1，2，3}，B={4，5，6}，对应关系如图．A．1B．2C．3D．4