Which of the following statements is accurate regarding soil unit weight?

Explanation

Option D is correct because when soil is submerged in water, the buoyant force reduces its effective weight, causing the unit weight to decrease. The other options are incorrect: dry soil has a lower unit weight than wet soil due to the absence of moisture (A), dry unit weight is always less than total unit weight because total unit weight includes moisture content (B), and submergence causes a decrease, not an increase, in unit weight (C).