As it is not given that the array is sorted or unsorted , so we assume it to be unsorted as it is more generic case..So for median finding we mean that we need to find the (n/2) th element in the array if :
The array were sorted..
So this is done easily using selection procedure ; a variant of quicksort by setting k = n/2..Hence we can do the same in O(n) time..
Hence B) is the correct answer