Most accepted theory of ageing is

Options

A. Death of brains cells
B. Non-functioning of `alpha`-cells in pancreas
C. Less RBC in blood
D. Non-functioning of thymus gland.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the most accepted theory of aging among the provided options.

2. **Analyzing the Options**:
- **Option 1: Death of Brain Cells**: This option is incorrect because brain cell death can occur at any age, not just in the elderly. It is not a specific indicator of aging.

- **Option 2: Non-functioning of Alpha Cells in Pancreas**: This option is also incorrect. Non-functioning alpha cells can lead to diabetes, which can affect individuals of any age, thus it is not a definitive aging factor.

- **Option 3: Less RBC in Blood**: This option is incorrect as well. A decrease in red blood cells (RBCs) can occur due to various conditions and is not exclusive to aging.

- **Option 4: Non-functioning of Thymus Gland**: This is the correct option. The thymus gland plays a crucial role in the immune system by producing T cells, which are essential for fighting infections. As people age, the function of the thymus gland declines, leading to a decrease in T cell production, which is widely accepted as a significant factor in the aging process.

3. **Conclusion**: The most accepted theory of aging is related to the non-functioning of the thymus gland, which affects the immune system and is a key factor in the aging process.

**Final Answer**: The most accepted theory of aging is the non-functioning of the thymus gland.

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