The nutrient solution in flowering culture hydroponics:

What is a hydroponic solution?

$A$: Jar for nutrient solution culture contains a split cover with holes which hold a bent tube for aeration.
$R$: Regular aeration of culture solution is necessary for proper growth and activities of roots.

Hydroponics is a technique of growing plants in a

Carefully observe the following figure.
$(a)$ Name the technique shown in the figure and the scientist who demonstrated this technique for the first time.
$(b)$ Name at least three plants for which this technique can be employed for their commercial production.
$(c)$ What is the significance of the aerating tube and feeding funnel in this setup?

The figure given below shows $..............$.