7. A square board is divided into $4 \times 4$ squares. Initially, all the squares are white. We want to color as many squares blue as possible, in such a way that each blue square has exactly one white neighbor (two squares are neighbors if they share a side). What is the maximum number of squares we can color blue?
A) 6
B) 8
C) 10
D) 12
E) 14
A7. D) 12 A filling with 12 blue squares where each blue square has exactly one white neighboring square can be seen in the figure. A coloring with more than 12 blue squares does not exist. With a coloring of 13 or more blue squares, there are at most 3 white squares. These white squares together have no more than $3 \times 4=12$ neighboring squares, so at least one blue square does not have a white neighboring square.

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