The number in each question bleow is to be codified in the following code:
Digit 7 2 1 5 3 9 8 6 4
Letter W L M S I N D J B
->  879341

Answer: C. DWNIBM

As given, 8 is coded as D,
7 as W,
9 as N,
3 as I,
4 as B   and
1 as M.
So, 879341 is coded as DWNIBM.