The annual rings are formed due to

Options

A. A. Uniform environmental conditions
B. B. Non-uniform environmental conditions
C. C. Absence of secondary growth
D. D.  Absence of primary growth

Answer

**Step-by-Step Solution:**

1. **Understanding Annual Rings**: Annual rings are concentric layers found in the cross-section of a tree trunk. Each ring represents one year of growth.

2. **Formation of Annual Rings**: Annual rings are formed due to the activity of the cambium layer, which produces secondary xylem (wood) and secondary phloem (bark).

3. **Cambium Activity**: The cambium is more active during certain seasons. In spring, it produces larger and more numerous xylem cells, leading to the formation of what is called "spring wood" or "early wood." In contrast, during autumn, the cambium is less active, producing smaller and fewer cells, known as "autumn wood" or "late wood."

4. **Seasonal Variation**: The variation in the size and number of cells produced in different seasons (spring vs. autumn) is due to non-uniform environmental conditions, such as temperature and moisture availability.

5. **Conclusion**: Since the formation of annual rings is influenced by these varying conditions, the correct answer to the question is that annual rings are formed due to **non-uniform environmental conditions** (Option B).

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