Letter series type of questions usually consists of a series of small letters which follow a certain pattern. However, some letters are missing from the series. These missing letters are then given in a proper sequence as one of the alternatives. The candidate is requitred to choose this alternative as the answer.
A _ B A C _ D _ B C D C _ 3 _ 2 _ 1 _ 4 ? ? ? ? d c _ _ b a c b _ _ _ _
Clearly, 2 corresponds to A.
Now, b corresponds to C and 4 corresponds to b.
So, 4 corresponds to C.
c corresponds to D and 3 corresponds to c.
So, 3 corresponds to D.
So, the reamaining number i.e., 1 corresponds to B.
Thus, BCDC corresponds to 1, 4, 3, 4.