Each alpha decay reduces Z by 2 and A by 4; two alpha decays therefore reduce Z by 4 and A by 8.

Half-life t1/2 = ln2 / λ ≈ 0.693 / (2.4×10^-8 s^-1) ≈ 2.9×10^7 s.

Alpha emission reduces the mass number A by 4 and the atomic number Z by 2, matching option D (determined from nuclear decay rules).

Typical atomic radius ~10^-10 m and nuclear radius ~10^-15 m yield a volume ratio on the order of 10^10.

a = b ≠ c with all angles 90° defines the tetragonal crystal system.

Absorbed dose D = energy/mass = 100 J / 2 kg = 50 Gy.

Emission of electrons from a metal when illuminated by photons is the photoelectric effect.

In the non-classical (classically forbidden) region the WKB solution is exponential (sum of exp(±∫κ dx/ħ) terms), and option B is the choice that contains the exponential terms.

Quantum tunneling explains alpha decay, allowing alpha particles to escape through the nuclear barrier.

Strangeness is not conserved in weak interactions, so it need not be conserved in all decays.