Answer: Option (c) is the correct answer.
Explanation:
A positron is denoted as [tex]^{0}_{+1}e[/tex], a neutron is denoted as [tex]^{1}_{0}n[/tex], an electron is denoted as [tex]^{0}_{-1}e[/tex], and a proton is denoted as [tex]^{1}_{1}p[/tex].
Therefore, when [tex]^{219}Rn[/tex] will decay into [tex]^{218}Rn[/tex] this means there occurs decrease in its mass number. Hence, it means a neutron will be releasing during this reaction.
The reaction will be as follows.
[tex]^{219}Rn \rightarrow ^{218}Rn + ^{1}_{0}n[/tex]
