Identify the letter–number cluster that completes the analogy. Apply the rule to each full number, not to its individual digits.
GH210 : IJ240 :: MN300 : ? :: WX650 : YZ680

The correct option is OP330.

To find the missing letter–number cluster, we analyze the logical rule applied to the letter portion and the numerical portion separately across the given analogy pairs: GH210 : IJ240 :: MN300 : ? :: WX650 : YZ680.

Step 1: Analyze the first pair (GH210 : IJ240)
• Letters: Moving forward by 2 positions in the alphabetical order:
G → I (+2)
H → J (+2)
• Number: Adding 30 to the full number:

$210+30=240$

Step 2: Verify the rule with the third pair (WX650 : YZ680)
• Letters: Moving forward by 2 positions:
W → Y (+2)
X → Z (+2)
• Number: Adding 30 to the full number:

$650+30=680$

Step 3: Apply the rule to find the missing cluster (MN300 : ?)
• Letters:
M + 2 positions = O
N + 2 positions = P
Thus, the letter cluster is OP.
• Number:

$300+30=330$

Combining the derived letters and number gives the final cluster OP330.