Option : (A)
Given that,
∠A = 140°
∠D = 60°
According to question,
∠A + ∠C = 2 (∠B + ∠D)
140 + ∠C = 2 (∠B + 60°)
∠B = \(\frac{1}{2}\)(∠C) + 10° ...(i)
We know,
∠A + ∠B + ∠C + ∠D = 360°
140° + \(\frac{1}{2}\)(∠C) + 10° + ∠C + 60° = 360°
\(\frac{3}{2}\)∠C = 150°
∠C = 100°
∠B = \(\frac{1}{2}\)(100°) + 10°
= 60°