Which is the unit matrix or identity matrix in the following?
1
\(\left( {\begin{array}{*{20}{c}} {1.0}&{0.0}&{1.0}\\ {0.0}&{1.0}&{0.0}\\ {1.0}&{0.0}&{1.0} \end{array}} \right)\)
2
\(\left( {\begin{array}{*{20}{c}} {1.0}&{0.0}&{0.0}\\ {1.0}&{0.0}&{0.0}\\ {1.0}&{0.0}&{0.0} \end{array}} \right)\)
3
\(\left( {\begin{array}{*{20}{c}} {0.0}&{1.0}&{0.0}\\ {0.0}&{1.0}&{0.0}\\ {0.0}&{1.0}&{0.0} \end{array}} \right)\)
4
\(\left( {\begin{array}{*{20}{c}} {1.0}&{0.0}&{0.0}\\ {0.0}&{1.0}&{0.0}\\ {0.0}&{0.0}&{1.0} \end{array}} \right)\)