Question

Which of the following is a defining characteristic of living organisms?
A. Growth
B. Ability to make sound
C. Reproduction
D. Response to external stimuli

Answer 1

Hint: A defining characteristic is a property held by all members of a class of objects that is so distinctive that it is sufficient to determine membership in that class.

Complete answer: Growth is not observed in some living organisms.
1. Ability to make sound is also not observed in lower animals.
2. Many living organisms are unable to reproduce. Therefore, growth, ability to make sound, and reproduction are not considered as defining characteristics of living organisms.
3. Response to external stimuli or to the environment in which an organism’s lives is the most important characteristic of any living organism.
4. Every organism shows a response to its surrounding environment.

Additional information: In physiology, a stimulus (plural stimuli) is a detectable form of change in the physical or chemical structure of an organism's internal or external environment. The ability of an organism or organ to detect external stimuli, so that an appropriate reaction can be formed, is called sensitivity.
1. All living organisms are made up of cells.
2. All living organisms need the energy to stay alive.
3. All living organisms maintain a stable internal environment.

So, the answer is D. Response to external stimuli

Note: A stimulus is a perceptible change in the interior or outside condition.
The capacity of a living being or organ to react to those changes is called irritability or responsiveness to stimulus.