Explanation : Here string length is 4 so we can create string of length 4 by 6 values. Suppose at first place we can arrange any value by 6 methods.so 6. then Remaining total numbers are 5 so we can arrange them by 5 methods at second place. then remaining total numbers are 4 so we can arrange them by 4 methods. now remaining total numbers are 3 and we can arrange them by 3 methods. so according to permutation technique. We multiply them i.e. 6*5*4*3=360. So, 'B'