题目

My son wastes a lot of time playing online games every day. Now I regret  ____the computer .     A.to buy    B. buying            C. to be buying       D. having bought   答案：B如图，反比例函数在第一象限内的图象经过菱形OABC的顶点A和C．若菱形OABC的面积为10，∠AOC=30°，则k的值为_____．