Write down the balanced nuclear equation for the beta emission of barium-138.

• A. ₅₆¹³⁸Ba → ₅₆¹³⁷Ba + ₀^-1e
• B. ₅₆¹³⁸Ba → ₅₇¹³⁸La + _-1⁰e
• C. ₁₃₈⁵⁶Ba → ₁₃₈⁵⁷La + _-1⁰e
• D. ₅₆¹³⁸Ba → ₅₅¹³⁸Cs + _-1⁰e

Answer: (B)