题目

--How is your grandfather now? --Oh, he _______for two weeks. A. died                B. has died        C. dead         D. has been dead 答案：D 解析: 略 判断下列命题是真命题还是假命题，若是真命题，说明为什么．若是假命题，请举反例说明． 在平面内，垂直于同一条直线的两条直线平行．