Find the missing couple of letters in the following series:
AZ, GT, MN, ? , YB	Choose the correct choice from the following choices:  A) SE  B) SM  C) SO  D) SH  E) SP
SH   SH   If you look closely, you will see that the first letter of every set is moving 6 alphabets forward while the second one is moving six alphabets backwards.
<result>D</result>
Find the missing couple of letters in the following series:
AZ, GT, MN, ? , YB