What is a lifetime friend?
A. Someone who always helps you out of difficulties.
B. Someone who understands you better than anyone else.
C. Someone who has experienced hardships with you.
D. Someone who together with you makes up a single soul in two bodies.
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What is the passage mainly about?
A. Three different stages of friendship.
B. Three different types of friendship in our life.
C. Three different ways of getting along with people.
D. Three different lessons on how to be good to your friends.
5．若A为6阶方阵，齐次方程组Ax=0基础解系中解向量的个数为2，则r(A)（）
A. 2
B. 3
C. 4
D. 5
设A为n阶方阵，r(A)
Ax=0只有零解
B.Ax=0的基础解系含r(A)个解向量
C.Ax=0的基础解系含n-r(A)个解向量
D.Ax=0没有解
视频中出现的第一座园林是以下哪座园林？
A. 拙政园
B. 留园
C. 狮子林
D. 耦园
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