Variables in the Wind Erosion Equation (WEQ, Woodruff and Siddoway, 1965: $E = f(I, K, C, L, V)$):

• $I$: Soil erodibility index (expressed as potential soil loss in tonnes/ha/year from an isolated, level, smooth, unsheltered field based on percentage of non-erodible aggregates $\gt 0.84\text{ mm}$).
• Soil erosivity relates to kinetic energy of rainfall/wind.
• Wind velocity is captured in the climatic factor ($C$).
• Wind duration is part of the climatic factor ($C$).
  
  Option breakdown:
• $I$ stands for soil erodibility index.
• Erosivity is climate/force related.
• Wind velocity is part of $C$.
• Wind duration is part of $C$.

According to Hans Jenny ($1941$), soil formation factors are $S = f(cl, o, r, p, t)$. Active factors supply energy to act on the soil system: Climate ($cl$) and Organisms/Biosphere ($o$). Passive factors are Parent material ($p$), Relief/Topography ($r$), and Time ($t$). Option analysis: (A) Time and Relief are passive factors. (B) Climate and Organisms are the active factors. (C) Time is passive. (D) Parent material is passive.

In laterization (ferrallitization), intense leaching of silica occurs, leaving the soil enriched with sesquioxides of iron and aluminium. In podzolization, organic acids leach iron and aluminium sesquioxides downward, leaving the surface horizon enriched in silica. Thus, lateritic soils are sesquioxide-enriched and podzolised soils are silica-enriched (statement iv). Option analysis: (A) (i) and (ii) are incorrect. (B) (i) and (iii) are incorrect. (C) (i) only is incorrect. (D) (iv) only is the correct answer.