What is the balanced nuclear equation when the isotope actinium-225 decays by alpha emission?

• A. ²²⁵₈₉Ac + ⁴₂He → ²²⁹₉₁Fr
• B. ²²⁵₈₉Ac → ²²¹₈₇Fr + ⁴₂He
• C. ²²⁵₈₉Ac → ²²⁹₉₁Pa + ⁴₂He
• D. ²²⁵₈₉Ac + ⁴₂He → ²²¹₈₇Ac

Answer: (B)