The document marks option B as correct; the percentage uncertainties from diameter and length combine to yield the indicated total (as shown).

Initial salt = 6×0.04 = 0.24 kg; after evaporating 1 kg water total mass = 5.0 kg, so salt% = 0.24/5.0 = 0.048 = 4.8%.

For ρ = Wa/(Wa - Ww) with Wa=10±0.1 and Ww=5±0.1, propagation gives δρ ≈ (WwδWa + WaδWw)/(Wa - Ww)^2 leading to ≈3% maximum percentage error.

With a least count of 1 mm, the measurement should be quoted to the nearest millimetre, i.e., 0.542 m.

The block indicates the absolute uncertainty equals the least count in this context, matching option B as marked in the OCR.

Uncertainty can be expressed as absolute, fractional, or percentage, so all types apply.

Combining contributions (from radius, resistance and length) gives approximately 16.7%+3.3%+0.2% ≈ 20% total percentage error.

For a volume depending on r^2 and l, percentage uncertainty is 2×(diameter uncertainty) + length uncertainty = 2×0.8% + 0.2% = 1.8%.

When quantities are multiplied or divided, their fractional (or percentage) uncertainties add, so fractional uncertainties are added.

Density ∝ m / l³, so %Δρ = %Δm + 3×%Δl = 3% + 3×2% = 9%.