1Each panel below shows one triangle. Moving from panel 1 to panel 3, the triangle's shading (darkness) changes by the same fixed amount at every step. Study the pattern, then choose the option that correctly completes the missing 4th panel.
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Answer: <svg xmlns="http://www.w3.org/2000/svg" width="150" height="232" viewBox="0 0 150 232"><rect x="0" y="0" width="150" height="232" fill="#ffffff"/><rect x="1" y="1" width="148" height="188" fill="#ffffff" stroke="#111827" stroke-width="2"/><polygon points="75.0,60.5 104.9,112.2 45.1,112.2" fill="#5c6472" stroke="#111827" stroke-width="2"/><rect x="0" y="188.0" width="150" height="44" fill="#111827"/><text x="75.0" y="219.0" font-size="22" font-weight="bold" font-family="Arial, sans-serif" text-anchor="middle" fill="#ffffff">B</text></svg>
Rule: the triangle's shading (darkness) increases by a constant step of 1 unit(s) per panel (shading-scale index). Panel 1 = shading level 1 of 6 (darker = higher), panel 2 = shading level 2 of 6 (darker = higher), panel 3 = shading level 3 of 6 (darker = higher). Adding the same step once more gives the missing panel: shading level 4 of 6 (darker = higher) — this is option B. Option C applies a step of 2 unit(s) instead of 1, over- or under-shooting the established rate of change. Option A shows the same shading (darkness) as panel 2, reversing the progression instead of continuing it forward. Option D has the correct shading (darkness) value but substitutes a diamond for the triangle, breaking the requirement that the same shape appear in every panel.
Rule: the triangle's shading (darkness) increases by a constant step of 1 unit(s) per panel (shading-scale index). Panel 1 = shading level 1 of 6 (darker = higher), panel 2 = shading level 2 of 6 (darker = higher), panel 3 = shading level 3 of 6 (darker = higher). Adding the same step once more gives the missing panel: shading level 4 of 6 (darker = higher) — this is option B. Option C applies a step of 2 unit(s) instead of 1, over- or under-shooting the established rate of change. Option A shows the same shading (darkness) as panel 2, reversing the progression instead of continuing it forward. Option D has the correct shading (darkness) value but substitutes a diamond for the triangle, breaking the requirement that the same shape appear in every panel.