The function f(x) = x² - 2x + 1 can be written as f(x) = (x-1)² by completing the square. Since any squared quantity is always non-negative, (x-1)² ≥ 0 for all real x. Therefore, the range of f(x) is [0, +∞), meaning all values from 0 to positive infinity, including 0 (when x = 1). Option C is incorrect because it excludes 0, which is achieved at x = 1. Option B incorrectly suggests the function is bounded above, but parabolas opening upward are unbounded. Option D excludes 0 and incorrectly shifts the starting point.