In the most simple words:-

¶ They are selected bcoz they have HIGH RATE OF RESPIRATION.

Selection of Germinating Seeds for Demonstrating Respiration
Respiration is a vital process in living organisms, including plants, where energy is produced by breaking down organic molecules. Germinating seeds are an excellent choice for demonstrating respiration due to the following reasons:

High Metabolic Activity:
Germinating seeds have a high metabolic rate as they are actively converting stored nutrients into energy for growth. This increased metabolic activity results in a more prominent respiration process, making it easier to observe and measure.

Rapid Oxygen Consumption:
During germination, seeds require a significant amount of oxygen to break down complex molecules and release energy. By measuring the rate of oxygen consumption, one can directly assess the level of respiration occurring in the seeds.

Visible Growth and Development:
Germinating seeds exhibit visible signs of growth, such as sprouting roots and shoots. This growth is fueled by the energy produced through respiration. By observing the growth of germinating seeds over time, one can directly correlate it with the respiratory activity taking place.

Simple Experimental Setup:
Using germinating seeds for respiration experiments is straightforward and requires minimal equipment. By placing germinating seeds in a closed container with a respirometer, one can easily measure the exchange of gases and determine the rate of respiration.

Education and Demonstration:
Demonstrating respiration using germinating seeds can be an engaging educational tool for students to understand the concept of cellular respiration. It provides a hands-on experience that allows students to witness the connection between plant growth and energy production.
In conclusion, the selection of germinating seeds for demonstrating respiration is ideal due to their high metabolic activity, rapid oxygen consumption, visible growth, simple experimental setup, and educational value. By using germinating seeds, one can effectively illustrate the process of respiration in living organisms.