第23题: [单项选择]A是m×n矩阵,AT是A的转置矩阵,若η1,η2,…,ηt是齐次方程组ATX=0的基础解系,则r A. 等于( )(A) t B. n-t C. m-t D. n-m 参考答案:C 答案解析:[考点] 矩阵的秩与齐次方程组基础解系含解向量的个数 [答案解析] A为m×n矩阵,则AT为n×m矩阵ATX=0是由n个方程,m个未知数组成的齐次
第27题: [单项选择]______ as it was at such a time, his work attracted much attention. A. Being published B. Published C. Publishing D. To be published 参考答案:B 答案解析:本题测试as引导的让步从句的倒装用法。在as引导的让步从句中.从句中的表语状语须提到as前,故B正确。C项语态不对,A项和D项时态不对,均应排除。