(A)____ is regarded as one of the most fundamental and conspicuous characteristics of a living being.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a term that is considered one of the most fundamental and noticeable characteristics of living beings.

2. **Identifying Key Characteristics of Living Beings**: Living organisms share several key characteristics, including:
- Growth
- Reproduction
- Sensitivity to the environment
- Metabolism
- Regulation of body fluids

3. **Focusing on Growth**: Among these characteristics, growth is highlighted as a fundamental trait. It is described as an irreversible change in size and cell number in an organism.

4. **Defining Growth**: Growth is not just an increase in size but also involves the development of the organism and its various parts. It is a clear and observable characteristic that distinguishes living beings from non-living entities.

5. **Conclusion**: Based on the analysis, the term that fills the blank is "growth".

**Final Answer**: (A) Growth is regarded as one of the most fundamental and conspicuous characteristics of a living being.

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