Option B: $\dfrac{1}{3}$
On a die, possible outcomes = {1, 2, 3, 4, 5, 6}. Composite numbers greater than 3 are 4 and 6 (2 outcomes). P = $\dfrac{2}{6} = \dfrac{1}{3}$.
Remember: composite numbers have more than two factors. Among 1–6, composites are 4 and 6 (4 = 2×2, 6 = 2×3). The number 1 is neither prime nor composite; 2, 3, 5 are prime. Since the question asks for composites greater than 3, only 4 and 6 qualify — giving 2 favourable outcomes out of 6.