
A.
1 
B.
O 
C.
1 
D.
2
Correct Answer: Option C
Explanation
Recall that a unit matrice is a diagonal matrix in which the elements in the leading diagonal is unity. Therefore,
I_{3} = (begin{pmatrix} 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 end{pmatrix})
I_{3} = (+1begin{vmatrix} 1 & 0 \ 0 & 1 end{vmatrix} – 0begin{vmatrix} 0 & 0 \ 0 & 1 end{vmatrix} + 0 begin{vmatrix} 0 & 1 \ 0 & 0 end{vmatrix} )
I_{3} = +1(1 – 0) – 0(0 – 0) + 0(0 – 0)
= 1(1)
= 1
There is an explanation video available below.