Question

Microorganisms act upon the dead plants to produce
(a)Sand
(b)Mushrooms
(c)Humus
(d)Wood

Answer 1

Decomposers are the microorganisms which act upon the dead plants and decompose them. The decomposed material produced by microorganisms provides fertility to the land.

Complete answer:
The microorganisms act upon the dead plants to produce humus. Humus is the top layer, most fertile part of the soil. Micro-organisms break down the complex structures of dead plants to simpler, easily usable components, which constitutes humus. As it isn't the most fertile part of it they are readily utilized by other plants for growing.

Additional Information: -The organisms which are capable of performing the process of decomposing are known as decomposers. These decomposers utilize most of the nutrients by themselves to procreate.
-Biopolymers such as chitin are structurally hard and cannot be utilized by any other organism until unless they are broken down to simpler complexes by decomposers.
-Decomposers are not producers in the food chain but they do not depend on any specific organisms to make their own energy, which means they consume the organic matter of a dead plant and leave the inorganic part for other organisms.
So, the correct answer is ‘humus’.

Note: -Even though humus is mainly composed of inorganic matter, they are rich in nitrogen which is an organic compound. They are also an agent in the recycling of nitrogen in the ecosystem.
-During heavy rain the nitrogen-rich topsoil gets washed away to the nearby water bodies, which takes away the fertility of the soil.
-This washing away of humus to water bodies causes eutrophication, where undesired microorganisms and algae multiply in the water bodies using the nitrogen available from the humus. This in turn reduces the oxygen content in the water for other organisms to use.