Conservation of current requires drift speed to vary inversely with cross-sectional area Steps:

• Electrons flow clockwise, so current is steady and constant through the plate.
• Uniform thickness implies constant height, but diagram likely shows width decreasing from right to left, reducing cross-sectional area A.
• Steady current I = n e A v_d, with charge density n and e constant.
• As A decreases from right to left, v_d must increase to maintain constant I.

Why B is correct:

• Drift speed v_d increases from right to left because I = n e A v_d requires v_d ∝ 1/A for constant I and n.

Why the others are wrong:

• A: Drift speed increases, not decreases, as A decreases.
• C: Number density n of conduction electrons remains uniform in a metal.
• D: Number density n does not vary; it's intrinsic to the metal.

Final answer: B