State the uses of hydroponics.

Mention the methods to study the mineral requirements in plants.

The technique of growing plants to maturity in a defined nutrient solution in the complete absence of soil is known as.............

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?

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

What does the given experimental set-up depict?
Choose the correct option.