Appeared in: 2025 (3 sets)
If f(x) = \begin{cases} \frac{\log (1 + ax) + \log (1 - bx)}{x}, & \text{for } x \neq 0 \\ k & , \text{for } x = 0 \end{cases} is continuous at x = 0, then the value of k is : (A) a (B) a + b (C) a - b (D) b