The term "rhizosphere" was given by Hiltner. The rhizosphere is the narrow region of soil that is directly influenced by the root system of plants. It is the area where roots release various substances and interactions occur between the roots and the soil microbes. Hiltner, a German scientist, first used the term in 1904 to describe the zone of soil around the roots that harbors a dense population of beneficial microorganisms. These microorganisms interact with the plant roots and contribute to important processes such as nutrient cycling and plant growth promotion. Garret and Alexopoulos are not associated with the term "rhizosphere." Therefore, the correct answer is option 3 - Hiltner.