Q.Pick out the correct pair :

Edaphic factors are the abiotic factors tied specifically to soil, and the dedicated study of soil is called pedology. Soil is the weathered superficial layer of the Earth's crust where plants root, forming gradually from parent rock through weathering (including biological weathering by bacteria, fungi, lichens and plants). Soil texture is described by particle-size class — clayey (<0.002 mm), silt (0.002–0.02 mm), loamy (0.002–2 mm, ~70% sand + 30% clay/silt, considered ideal for cultivation), and sandy (0.2–2 mm) — and soil stratifies with depth into a soil profile of horizons: the organic O-horizon (humus, split into freshly-fallen O1 and decomposed O2), the leached A-horizon (topsoil, split into organic-rich A1 and mineral-rich A2), the accumulation B-horizon (subsoil, poor in humus, rich in iron/aluminium/silica clay), the partially-weathered C-horizon (parent rock fragments), and the bedrock R-horizon. Key edaphic sub-factors include soil moisture/soil water (capillary water between soil particles is the most important form available to plants), soil reaction (pH; crop plants do best at 5.5–6.8), soil nutrients (fertility, as mineral/organic ions), soil temperature (low temperature reduces root water/solute uptake), …