The inert pair effect refers to the phenomenon where the valence s-electrons of heavier elements (in the p-block) are less reactive compared to their corresponding p-electrons. This effect becomes more pronounced as we move down a group in the periodic table.

Now, let's analyze the elements given in the question:

a) Germanium (Ge):
- Atomic number = 30
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p²
- Valence electrons = 4s² 4p²

b) Lead (Pb):
- Atomic number = 82
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p²
- Valence electrons = 6s² 6p²

c) Silicon (Si):
- Atomic number = 14
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p²
- Valence electrons = 3s² 3p²

d) Tin (Sn):
- Atomic number = 50
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p²
- Valence electrons = 5s² 5p²

Analysis:
- The inert pair effect becomes more pronounced as we move down a group in the periodic table.
- Lead (Pb) has the highest atomic number among the given elements, indicating that it is located at the bottom of its group (group 14).
- Lead (Pb) has the valence electron configuration of 6s² 6p², where the 6s electrons are further away from the nucleus compared to the 6p electrons.
- The increased distance from the nucleus results in poor shielding of the 6s electrons by the inner shells, making them less reactive.
- Therefore, lead (Pb) exhibits the maximum inert pair effect among the given elements.

Hence, the correct answer is option 'B' (Pb).