Sum of two skew-symmetric matrices is always  matrix.

A matrix which is not a square matrix is called a _____matrix.

Matrix multiplication is _____over addition.

If $A$ is a skew-symmetric matrix, then $A^2$ is a_____ matrix.

If $A$ and $B$ are square matrices of the same order, then $(AB{)}^{\text{'}}=k\left(B^{\text{'}}{A}^{\text{'}}\right)$, $k=$_____

If $A$ and $B$ are square matrices of the same order, then

$(kA{)}^{\text{'}}=$_____$A\text{'}$  (where $k$ is any scalar).