The unstable nucleus${ }_{82}^{212}\mathrm{Pb}$ decays with $\mathrm{\beta }$-particle emission, having a half-life of 10 h. From this it follows that the
A : mass number of the product is 212
B : atomic number of the product is 81
C : fraction of the original isotope remaining after 20 h is $\frac{1}{4}$
D : product nucleus formed belongs to same group
Select the correct alternate.

• A

  A,B and C

• B

  A and C

• C

  B and D

• D

  Only D