The correct option is A 4
r1r2r3r4r5⎡⎢
⎢
⎢
⎢
⎢
⎢⎣1−1000001−1001−100−100010001−1⎤⎥
⎥
⎥
⎥
⎥
⎥⎦
r1→r1+r2+r3+r4+r5
We get,
A=⎡⎢
⎢
⎢
⎢
⎢
⎢⎣00000001−1001−100−100010001−1⎤⎥
⎥
⎥
⎥
⎥
⎥⎦5×5
So, |A|=0
Hence rank(A)<5
But now another row is not becoming zero.
So at least one 4× 4 matrix in A is not zero
Hence Rank = 4