Which of the following is a defining characteristic of living organisms ?

Options

A. Growth
B. Ability to make sound
C. Reproduction
D. Response to external stimuli

Explanation

To determine the defining characteristic of living organisms, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: Although the options are not provided, we can consider common characteristics of living organisms such as growth, reproduction, response to stimuli, and ability to make sound.

2. **Analyze Each Characteristic**:
- **Growth**: While living organisms grow, non-living things can also increase in size (e.g., a pile of garbage). Thus, growth alone is not a defining characteristic.
- **Reproduction**: While reproduction is a key feature of living organisms, some organisms (like mules) are sterile and cannot reproduce. Therefore, it is not universally applicable.
- **Ability to Make Sound**: Non-living objects can produce sound (e.g., a table creaking), so this is not a defining characteristic of living organisms.
- **Response to External Stimuli**: All living organisms, from prokaryotes to eukaryotes, respond to external stimuli in various ways (e.g., plants bending towards light, animals fleeing from danger). This characteristic is universal among living organisms.

3. **Conclusion**: Based on the analysis, the defining characteristic of living organisms is their ability to respond to external stimuli.

### Final Answer:
The defining characteristic of living organisms is **response to external stimuli**.

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