Answer:
![_(84)^(208)Po](https://img.qammunity.org/2019/formulas/physics/high-school/2axceb9ybm9n53uspdi22f5isapvixlc9t.png)
B is correct.
Step-by-step explanation:
Given the equation
![_(86)^(212)Rn\rightarrow_(2)^(4)He](https://img.qammunity.org/2019/formulas/physics/high-school/26ejf228lp1v4jx5kuajoenj46x3o7ewvq.png)
According to alpha emission
Alpha emission is a radioactive decay in which the atomic nucleus emit the alpha particle and formed a new nucleus whose mass number reduced by four and atomic number reduced by two.
Therefore,
Po is the new nucleus.
![_(86)^(212)Rn\rightarrow_(2)^(4)He+_(84)^(208)Po](https://img.qammunity.org/2019/formulas/physics/high-school/ltmeeklp8isjeo539wxra8xn8rcfsgat38.png)
Where, Rn = Radon
Po= polonium