Triangular Matrix

Q. Square matrix $[a_{ij}{]}_{n\times n}$ will be an upper triangular matrix, if

1. $a_{ij}\ne 0$, for i>j
2. $a_{ij}=0$, for i>j
3. $a_{ij}=0$, for i<j
4. $Noneofthese$

Q. If $\left[\begin{array}{cccc}1& 0& 0& 0\\ 2& 3& 0& 0\\ 4& 5& 6& 0\\ 7& 8& 9& 10\end{array}\right]$, then A is

1. A lower triangular matrix
2. None of these
3. An upper triangular matrix
4. A null matrix

Q. The matrix $\left[\begin{array}{ccc}2& 5& -7\\ 0& 3& 11\\ 0& 0& 9\end{array}\right]$ is known as

1. Symmetric matrix
2. Diagonal matrix
3. Upper triangular matrix
4. Skew symmetric matrix