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UKMT Junior Mathematical Challenge, 2017

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Mathias is given a grid of twelve small squares. He is asked to shade grey exactly four of the small squares so that his grid has two lines of reflection symmetry. How many different grids could he produce?

(A) $2$ (B) $3$ (C) $4$ (D) $5$ (E) $6$

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