Passage Three Questions 33 to 35 are based on the passage you have just heard.
A. It always expresses the message efficiently. B. It usually doesn’t match the language.
B. C. It sometimes isolates a meaning. D. It often shows the speaker’s true emotions.
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I first met Lisa three years ago. She (work) ______ at a radio shop at the time.
We would appreciate it if you could confirm your participation at your earliest conversation.
Kindly report to the management any inattention on the part of any employee.
设A为m阶实对称矩阵且正定,B为m×n阶实矩阵,BT为B的转置矩阵,试证BTAB为正定矩阵的充分必要条件是矩阵B的秩r(B)=n.