Which of the following recurrence relation can be solved using Master theorem?

The correct option is D. Master theorem applies to recurrences of the form T(n) = aT(n/b) + f(n), where a >= 1, b > 1, and f(n) is a positive function. T(n) = 2T(n/2) + 1 perfectly satisfies these conditions (a=2, b=2, f(n)=1). Other options fail due to negative terms, non-constant coefficients, or violating polynomial variance conditions.