Answer the following questions regarding γ-emission in radioactive decay processes.
a. (i) Explain why the emission of a γ-ray does not alter the mass number or atomic number of a nucleus.
b. (ii) A certain nucleus undergoes an α-decay forming daughter D₁, which almost instantaneously emits a γ-ray to form D₂. Compare the values of A and Z for D₁ and D₂, giving reasons for your answer.
c. (iii) State one practical consequence of γ-emission for radiation shielding required in nuclear laboratories.