Calculate the percentage of water in a soil sample given the following measurements: Mass of crucible = 10g, Mass of crucible + soil before heating = 29g, Mass of crucible + soil after heating = 18g.

Mass of wet soil = (Mass of crucible + soil before heating) - Mass of crucible
Mass of wet soil = 29 g - 10 g = 19 g

Mass of dry soil = (Mass of crucible + soil after heating) - Mass of crucible
Mass of dry soil = 18 g - 10 g = 8 g

Mass of water = Mass of wet soil - Mass of dry soil
Mass of water = 19 g - 8 g = 11 g

Percentage of water = $\frac{\text{Mass of water}}{\text{Mass of wet soil}} \times 100\%$
Percentage of water = $\frac{11 \text{ g}}{19 \text{ g}} \times 100\%$
Percentage of water $\approx 0.5789 \times 100\%$
Percentage of water $\approx 57.89\%$

Comparing this to the given options:
A. 20%
B. 25%
C. 40%
D. 57.9%

The closest option is D.

The correct option is D.