Hydroponics is a system of growing plants in

Growing plants in a nutrient solution,known as hydroponics:

Hydroponics is a method of

Cultivation by sand culture is also called

Hydroponics has been shown to be a successful technique for growing plants. Yet,most crops are still grown on land. Why?

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?