I have a beak, wings and feathers. I can_爱下问搜题

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问题选择题

I have a beak, wings and feathers. I can swim. I am a . [ ]

A. fish

B. duck

C. dog

D. cow

答案

B

问答题

设A，B，C是n阶方阵，满足r(C)+r(B)=n，(A+E)C=O，B(A^T-2E)=O．
证明：A～Λ，并求Λ及|A|．

问答题

简述领导者在接待中的沟通技巧。