A complete pit is

Options

A. Depression in secondary wall
B. Pit chamber and primary wall
C. Pit chambers of two adjacent cells and pit membrane
D. Pit chamber, primary wall and middle lamella

Answer

To solve the question "A complete pit is," we need to analyze the options provided and understand the structure and function of pits in plant cells.

### Step-by-Step Solution:

1. **Understanding the Definition of a Pit**:
- A pit is a structure found in the cell walls of plant cells, particularly in the secondary cell wall. It allows for communication and transport between adjacent cells.

2. **Identifying Components of a Complete Pit**:
- A complete pit consists of three main components:
- **Pit Chambers**: These are the hollow areas in the secondary cell walls of two adjacent cells.
- **Pit Membrane**: This is the thin layer that separates the pit chambers of the two adjacent cells.
- **Pit Opening**: This allows for the transport of substances between the pit chambers.

3. **Analyzing the Options**:
- **Option 1**: Depression in secondary cell wall - This describes a feature of a pit but does not encompass all components of a complete pit.
- **Option 2**: Pit chamber in primary wall - This is incorrect because pits are associated with the secondary cell wall, not the primary wall.
- **Option 3**: Pit chambers of two adjacent cells and pit membrane - This accurately describes a complete pit, including both chambers and the membrane.
- **Option 4**: Pit chamber, primary wall, and middle lamella - This is incorrect as it includes components that are not part of a complete pit.

4. **Conclusion**:
- Based on the analysis, the correct answer is **Option 3: Pit chambers of two adjacent cells and pit membrane**.

### Final Answer:
A complete pit is **Option 3: Pit chambers of two adjacent cells and pit membrane**.