Growth in living being is called:

Options

A. accretion
B. interaction
C. aggregation
D. intussusception

Answer

### Step-by-Step Solution:

1. **Understanding Growth in Living Beings**:
- Growth in living beings refers to the increase in size or mass of an organism. This can occur through various processes.

2. **Accretion**:
- Accretion is a type of growth where external parts of an organism accumulate over time. For example, the secondary cell wall in plants grows through accretion as new materials are added to it.

3. **Interaction**:
- Interaction refers to the mutual effect between two entities, which is not directly related to growth. For instance, the interaction between a magnet and an iron nail does not contribute to the growth of either.

4. **Intussusception**:
- Intussusception is another form of growth where new materials are deposited within existing structures, such as the cell wall. This process involves the deposition of new materials between the components already present.

5. **Cell Elongation**:
- Cell elongation is a crucial aspect of growth, particularly in plants. It involves the expansion of cells, which contributes to the overall growth of the organism.

6. **Conclusion**:
- Among the options discussed, the correct term that describes growth in living beings is **Intussusception**, as it involves the deposition of new materials within existing structures, leading to growth.

### Final Answer:
- **Growth in living beings is called Intussusception.**