It is told the matrix is 5⨉6 matrix with order 4
So, order 4 means it is 4⨉6 matrix
It has linearly independent 4 rows 6 columns
Here (A) and (B) false
Now Among C) and D)
In C) Q=5⨉6 Matrix Qt = 6⨉5
QQt will give 5⨉5 matrix
but 5 th row reduces and matrix will be 4⨉5
Again determinant will be 0 and matrix will be non invertable
D) is perfect to be invertable