1. **Problem:** Identify the correct expansion of the expression $(a - b)^2$. 2. **Formula:** The expansion of $(a - b)^2$ is given by: $$ (a - b)^2 = a^2 - 2ab + b^2 $$ This follows from the binomial expansion rule $(x - y)^2 = x^2 - 2xy + y^2$. 3. **Explanation:** - Option (a) is incorrect because it has a plus sign instead of a minus. - Option (b) matches the correct formula. - Option (c) is incorrect; it represents a difference of squares, not a square of a difference. - Option (d) is incorrect; it mixes signs incorrectly. **Final answer:** (b) $(a - b)^2 = a^2 - 2ab + b^2$