Concept:For a finite limit when the denominator tends to zero, the numerator must also contain the same repeated factor.Explanation:The denominator is x2−2x+1=(x−1)2.Since the limit is finite, the numerator must have (x−1)2 as a factor.As the numerator is a monic cubic polynomial, write x3+ax2+bx+c=(x−1)2(x+k).Then limx→1(x−1)2(x−1)2(x+k)=limx→1(x+k)=1+k.Given that the limit equals 2026, we have 1+k=2026, so k=2025.Now expand: (x−1)2(x+2025)=x3+2023x2−4049x+2025.Comparing coefficients with x3+ax2+bx+c, we get a=2023 and c=2025.Therefore, a−c=2023−2025=−2.Answer:Option D, −2.