Given polynomials:
\[
P_1(x) = 2x^3 + 5x^2 - 2x - 5
\]
\[
P_2(x) = 3x^3 - x^2 - 3x + 1
\]
Using the polynomial division method, we find that the remainder is:
\[
x^2 - 1
\]
Thus, the HCF of both polynomials is:
\[
x^2 - 1 = (x - 1)(x + 1)
\]
Thus, the correct answer is \( x^2 - 1 \).