Timber-line is

Options

A. Edge of forest beyond which trees occur in close canopy
B. Altitude or latitude beyond which no trees occur
C. Altitude or latitude at which timber trees grow
D. Boundary between grassland and forest.

Answer

### Step-by-Step Solution:

1. **Understanding Timberline**:
- Timberline refers to a specific boundary in nature where trees can no longer grow due to environmental conditions.

2. **Identifying Key Characteristics**:
- It is determined by factors such as altitude (height above sea level) or latitude (distance from the equator).
- Beyond this line, the conditions become unfavorable for tree growth, which can include factors like temperature, soil quality, and moisture availability.

3. **Evaluating Options**:
- The question provides several options to define timberline:
- A) Edge of forest beyond which trees occur in close canopy
- B) Altitude or latitude beyond which no trees occur
- C) Altitude or latitude at which timber trees grow
- D) Boundary between grassland or forest
- Among these options, we need to find the one that accurately describes timberline.

4. **Selecting the Correct Definition**:
- The most accurate definition of timberline is **B) Altitude or latitude beyond which no trees occur**. This option clearly states that beyond this point, trees cannot survive.

5. **Conclusion**:
- Therefore, timberline is defined as the altitude or latitude beyond which no trees can occur due to unfavorable environmental conditions.