题目

Houses in China's big cities are so unreasonably expensive that generally young couples can't afford _______ without their parents' financial support. A . that B . it C . any D . one 答案：D对于任意实数a，b，c，d，命题①若a＞b，c≠0，则ac＞bc；②若a＞b，则ac2＞bc2③若ac2＞bc2，则a＞b；④若a＞b，则；⑤若a＞b＞0，c＞d，则ac＞bd．其中真命题的个数是（ ）A．1B．2C．3D．4