题目

—Why didn’t he come to the meeting? —The reason           this was         he forgot． A．about; why          B．for; why       C．for; that           D．about; that 答案：C18．已知一次函数y=x-2与x轴，y轴分别交于点A和点B（1）求点A，点B的坐标，及△OAB的面积；（2）在坐标轴上确定一点C，使△ABC是直角三角形；（3）在坐标系中确定一点D，使点A、O、B、D四点构成的四边形为平行四边形．