Answer A) is correct. Let's see, why. The loop will be over the index of the array assigning the value uf arr[loopindex] to i and setting arr[i]=0.
loopindex arr-content before arr-content after
0 1,2,3,4 i=1 1,0,3,4
1 1,0,3,4 i=0 0,0,3,4
2 0,0,3,4 i=3 0,0,3,0
3 0,0,3,0 i=0 0,0,3,0