Answer
$A=\left[\begin{array}{lllll}
0 & a_{12} & a_{13} & a_{14} & a_{15}\\
a_{21} & 0 & a_{23} & a_{24} & a_{25}\\
a_{31} & a_{32} & 0 & a_{34} & a_{35}\\
a_{41} & a_{42} & a_{43} & 0 & a_{45}\\
a_{51} & a_{52} & a_{53} & a_{54} & 0
\end{array}\right]$
Work Step by Step
The elements $A_{ii}$ in a square n$\times$n matrix form the main diagonal.
Here, the main diagonal has zero entries:
$A=\left[\begin{array}{lllll}
0 & a_{12} & a_{13} & a_{14} & a_{15}\\
a_{21} & 0 & a_{23} & a_{24} & a_{25}\\
a_{31} & a_{32} & 0 & a_{34} & a_{35}\\
a_{41} & a_{42} & a_{43} & 0 & a_{45}\\
a_{51} & a_{52} & a_{53} & a_{54} & 0
\end{array}\right]$
