A square sheet of transparent paper with a printed chevron motif pointing to the upper-right corner is folded in half along its vertical centerline from right to left, and then folded in half along its horizontal centerline from bottom to top. How many layers of paper exist in the final folded square, and how does the chevron orientation compare across layers?

(A) 4 layers, with alternate layers exhibiting left-right and top-bottom mirror reflections

(B) 2 layers, with identical unreflected chevrons

(C) 8 layers, with all chevrons aligned in the original orientation

(D) 4 layers, with zero reflection across any layer

Answer Key:

A

### 5-Stage Derivation & Analytical Solution: 1. **Stage 1: Layer Doubling Law:** A sheet folded once has $2^1 = 2$ layers; folded twice orthogonally has $2^2 = 4$ layers. 2. **Stage 2: Spatial Chiral Symmetry:** A vertical fold reflects the $x$-coordinates ($x \to -x$), creating a lateral mirror reflection. A horizontal fold reflects $y$-coordinates ($y \to -y$), creating an inverted mirror reflection. 3. **Stage 3: Conclusion:** 4 layers are produced, and the motifs across opposing folds exhibit alternating bilateral reflections. 4. **Stage 4: Distractor Elimination:** Option B has wrong layer count. Options C and D ignore geometric mirror inversion. 5. **Stage 5: Selection:** Option A is uniquely correct.

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