Annual ring is formed by:
a) Early wood
b) Early wood + late wood
c) Heart wood + sap wood
d) Cork + cork cambium

Options

A. Early wood
B. Early wood + late wood
C. Heart wood + sap wood
D. Cork + cork cambium

Answer

To solve the question "Annual ring is formed by:", we need to analyze the options provided and understand the concept of annual rings in plants.

### Step-by-Step Solution:

1. **Understanding Annual Rings**:
- Annual rings are layers of growth in the trunk of a tree that represent one year of growth. Each ring consists of two parts: early wood and late wood.

2. **Identifying Early Wood**:
- Early wood (also known as spring wood) is formed during the favorable growing season, typically the rainy season. It is characterized by larger vessels and thinner walls, allowing for efficient water transport.

3. **Identifying Late Wood**:
- Late wood (also known as autumn wood) is formed during the less favorable growing season, such as winter or dry summer. It has smaller vessels and thicker walls, indicating slower growth.

4. **Combining Early Wood and Late Wood**:
- The annual ring is formed by the combination of early wood and late wood. Together, they represent the growth that occurs throughout the year, with early wood indicating rapid growth and late wood indicating slower growth.

5. **Evaluating Other Options**:
- Heart wood and sap wood do not directly form the annual ring; they are parts of the tree's structure. Heartwood is the older, non-conducting part of the wood, while sapwood is the younger, active part that conducts water.
- Cork and cork cambium are related to the outer protective layer of the tree and do not contribute to the formation of annual rings.

6. **Conclusion**:
- Based on the understanding that annual rings are formed by the combination of early wood and late wood, the correct answer is **b) Early wood + late wood**.

### Final Answer:
**b) Early wood + late wood**