下面说法正确的是（ABD）。 A: 对给定的n×n常值矩阵A，有<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/303dacf53d6143c2b28f05f011cccd4d.png" /> B: 当A为对角线矩阵，即A=diag{<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/c6add3ff591a49618a099f987b66ac9b.png" />}时，有<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/daf51358ae6a4eefbdd513874b1f0024.png" /> C: 当A具有如下形式<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/d35669dfbff8484ea1da422c1c05a134.png" />,有<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/122dc0b2302840628b70f41d6200c101.png" /> D: 当A具有如下形式<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/061f1e154a43492c846419cd29919f63.png" />,有<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/fe069d53e0c74e3f863b774fd4c94ad0.png" />