Passage Two
A. Because television is cheaper to purchase.
B. Because people could see the scene and the figures in movements.
C. Because television provides comfort to people.
D. Because television makes some actors and actress known to common people.
Passage One
A. It can’t make people feel good.
B. People can’t sleep well after the exercise.
C. It makes people feel good.
D. It helps people lose weight.
设A是n阶矩阵，α1，α2，…，αn是n维列向量，其中αn≠0，若Aα1=α2，Aα2=α3，…，Aαn-1=αn，Aαn=0． 证明α1，α2，…，α3线性无关；
设A，B均为n阶方阵，且A为可逆矩阵，B为不可逆矩阵，A*，B*分别为A，B的伴随矩阵，则______．
A*+B*必为可逆矩阵
B. A*+B*必为不可逆矩阵
C. A*B*必为可逆矩阵
D. A*B*必为不可逆矩阵
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