Answer:
Correct Answer is Option (D)
Step-by-step explanation:
The stable atom is (D) ₆₄Gd¹⁴⁷.
Positron is radioactive decay. Positron is a type of beta particle β⁺.
Positron emission decreases proton number relative to neutron number, positron decay results in nuclear transmutation, changing an atom of one chemical element with an atomic number that is less by one.
Terbium on positron emission produces Gadolinium with one atomic number less than Terbium. So, the positron emission reaction is as shown below:
Tb¹⁴⁷→ ₆₄Gd¹⁴⁷ + ₁e⁰
Hope I helped you out :D