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

Answer

To determine the defining characteristic of living organisms from the given options, we will analyze each option step by step.

### Step 1: Analyze the Options
We have four options to consider:
- a) Growth
- b) Ability to make sound
- c) Reproduction
- d) Response to external stimuli

### Step 2: Evaluate Each Option
1. **Growth**: While growth is a characteristic of living organisms, it can also be observed in non-living things (like crystals). Thus, it is not a definitive characteristic.

2. **Ability to make sound**: This is not a universal characteristic of all living organisms. Not all organisms can make sound, so this option does not qualify as a defining characteristic.

3. **Reproduction**: Reproduction is indeed a characteristic of living organisms, but some organisms can reproduce asexually or not at all. Therefore, it is important but not definitive.

4. **Response to external stimuli**: This is a fundamental characteristic of living organisms. All living organisms respond to changes in their environment, which is crucial for survival.

### Step 3: Conclusion
After evaluating all options, the most defining characteristic of living organisms is **d) Response to external stimuli**. This characteristic is essential for the survival and adaptation of living organisms in their environment.

### Final Answer
The correct option is **d) Response to external stimuli**.

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