Question

Microorganism act upon a dead plant to produce:
A. Humus
B. Mushroom
C. Wood
D. sand

Answer 1

It refers to the amorphous component of soil organic matter without the "cellular cake structure typical of plants, micro-organisms or animals." The bulk density of the soil is greatly affected and contributes to its retention of moisture and nutrients.

Complete answer:
To create humus, micro-organisms work on the dead plants. The microorganisms that turn dead plants and animals into humus, such as bacteria and fungi, are known as decomposers. Humus provides many beneficial minerals and nutrients for a good soil.
Different microorganisms, such as algae, amoeba, etc., break down different dead plants and animals and create many things, including humus.
It is a way for nature to break down contaminants in order not to pollute the soil. The humus or other substances that they create will later be used for different things.
Non-living humus, finely broken organic matter in soil, derived from microbial decomposition of plant and animal substances. Humus is made up of around 60 percent carbon, 6 percent nitrogen, and smaller quantities of phosphorus and sulphur, varying in colour from brown to black. Its components are converted into forms accessible by plants as humus decomposes.

Additional Information: Mushrooms are a fungal type. The part of the mushroom that develops and disperses spores is the structure that you usually see above the ground. Each spore is a single cell capable of sending out a hypha that grows into a group and forms a mycelium of its own.
Sand is a granular substance consisting of rock and mineral particles which are finely separated. It is distinguished by size, being finer than gravel and coarser than silt. Sand may also apply to a soil or soil type of textural class; i.e., soil containing by mass more than 85% of sand-sized particles. Depending on local rock sources and conditions, the composition of sand varies, but in inland continental settings and non-tropical coastal settings, the most common constituent of sand is silica, usually in the form of quartz.
Wood is a structural tissue found in the stems and roots of trees and other woody plants that is porous and fibrous. It is an organic material, a natural composite of tension-strong cellulose fibres that is embedded in a lignin matrix that prevents compression. Wood is often classified in the stems of trees as only the secondary xylem, or it is more generally defined to include the same type of tissue elsewhere, as in the roots of trees or shrubs.
So, the correct answer is humus’.

Note: Depending on the degree of its penetration into the mineral soil, the types of species involved in its decomposition, and the vegetation from which it is extracted, Humus is graded into mor, mull, or moderate formations. Humus is valued by farmers and gardeners because it provides important nutrients for plant growth, enhances the absorption of soil water, and improves soil workability.