Option A is correct
a is 3D array with size [3][3][3]
Therefore each 2D array contains 9 elements, we have 3 such arrays
0th 2D array have {1,2,3,4,5,6,7,8,9}
1st 2D array have {10,11,12,13,14,15,16,17,18}
2nd 2D array have {19,20,21,22,23,24,25,26,27}
each 2D array is collection of 1D array. we have 3 one dimensional arrays in one 2D
$\therefore \{\;\;{\underset{k=0,1,2\;\;}{\underbrace{1,2,3}}},\underset{k=0,1,2\;\;}{\underbrace{4,5,6}},\underset{k=0,1,2\;\;}{\underbrace{7,8,9}}\;\;\},$
$ \{{\underset{k=0,1,2\;\;}{\underbrace{10,11,12}}},\underset{k=0,1,2\;\;}{\underbrace{13,14,15}},\underset{k=0,1,2\;\;}{\underbrace{16,17,18}\}},$
$\{{\underset{k=0,1,2\;\;}{\underbrace{19,20,21}}},\underset{k=0,1,2\;\;}{\underbrace{22,23,24}},\underset{k=0,1,2\;\;}{\underbrace{25,26,27}\}}$
when i=0, j=0, output = {1,2,3}
when i=1, j=0, output = {10,11,12}
when i=2, j=0, output = {19,20,21}