单项选择题 给定矩阵,若是齐次线性方程组的基础解系,则( )。A. 4B. 3C. 2D. 1

单项选择题 The only one reason writers write is to communicate with and affect as many people as possible. Translation expands that number exponentially, allowing more and more readers to be touched by an author's work. A、正确 B、错误

未知题型 若室内电线或设备着火，不应采用()灭火 　　A.干砂土　　B.二氧化碳　　C.四氯化碳　　D.泡沫灭火器