The wood of commerce is
(a) sap-wood (alburnum)
(b) heart wood( duramen)
(c) spring wood
(d) autumn wood

Options

A. sap-wood (alburnum)
B. heart wood( duramen)
C. spring wood
D. autumn wood

Answer

To determine which type of wood is known as the "wood of commerce," we need to analyze the options provided:

1. **Understanding the Options**:
- (a) **Sap-wood (alburnum)**: This is the outer, living part of the wood that is involved in the conduction of water and nutrients. It is not typically used for commercial purposes.
- (b) **Heart wood (duramen)**: This is the inner, dead part of the wood that provides structural support. It is known for its durability and resistance to decay, making it suitable for various commercial applications.
- (c) **Spring wood**: This refers to the wood produced during the spring season, which is generally softer and less dense.
- (d) **Autumn wood**: This refers to the wood produced during the autumn season, which is typically denser than spring wood but not specifically known for commercial use.

2. **Identifying the Wood of Commerce**:
- The term "wood of commerce" generally refers to wood that is commercially valuable and widely used in construction, furniture making, and other industries.
- Heartwood (duramen) is recognized for its strength, durability, and resistance to decay, making it ideal for these purposes.

3. **Conclusion**:
- Based on the definitions and characteristics of each type of wood, the correct answer is **(b) heart wood (duramen)**, as it is the wood that is commercially valuable.

### Step-by-Step Solution:
1. Analyze each option provided in the question.
2. Understand the characteristics of sapwood, heartwood, spring wood, and autumn wood.
3. Identify which type of wood is known for its commercial value and strength.
4. Conclude that heartwood (duramen) is the correct answer.