1. BQ : The positions of letters in the alphabet are B = 2, Q = 17.
   Difference = 17−2=15

2. RB : The positions are R = 18, B = 2.
   Difference = 18−2=16

3. CP : The positions are C = 3, P = 16.
   Difference = 16−3=13.

4. LG : The positions are L = 12, G = 7.
   Difference = 12−7=5

Odd One Out: LG

The difference in letter positions for LG (5) is distinctly different from the others, which have larger differences (13, 15, 16).