The image shows three sets of 2x2 number grids with lines connecting the top and bottom pairs, followed by a multiple-choice question asking for a missing number represented by a "?".

Observing the pattern:

1. First grid:

   • Top row: 3, 6
   • Bottom row: 2, 1
   • The numbers in the bottom row seem to result from the difference between the top row numbers:
     • $6 - 3 = 3$, $6 - 2 = 4$

2. Second grid:

   • Top row: 4, 4
   • Bottom row: 1, 4
   • relationships between