Microbes added to soils to decrease the level of contaminants from root area of the plants is called as _________________.

Correct option is A

Bioaugmentation involves adding specific microorganisms to the soil that can degrade or neutralize contaminants. This process helps in reducing the levels of pollutants in the soil and improving the quality of the rhizosphere for plant growth.
Examine each option:
(a) Bioaugmentation: Correct; this process involves adding microorganisms to degrade contaminants in the soil.
(b) Rhizosphere Phytoremediation: Incorrect; refers to the use of plants and their associated microorganisms to remove contaminants.
(c) Bio Drainage: Incorrect; involves the use of plants to lower groundwater levels, not specifically for contaminant removal.
(d) Soil Enhancement: Incorrect; a broader term that includes various practices to improve soil quality, not specific to contaminant removal.