Which of the following show selective permeability?

Options

A. Cell membrane
B. Cell wall
C. Cytoplasm
D. Protoplasm

Answer

### Step-by-Step Solution:

1. **Understanding Selective Permeability**:
- Selective permeability is a property of certain membranes that allows only specific substances to pass through while blocking others. This is crucial for maintaining the internal environment of the cell.

2. **Identifying the Options**:
- The options given are:
- A) Cell membrane
- B) Cell wall
- C) Cytoplasm
- D) Protoplasm

3. **Analyzing Each Option**:
- **Cell Membrane**:
- The cell membrane (or plasma membrane) is known for its selective permeability. It is composed of a phospholipid bilayer, which has hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. This structure allows nonpolar molecules to pass through easily while polar molecules require assistance (active transport or facilitated diffusion).
- **Cell Wall**:
- The cell wall is generally permeable and does not selectively filter substances. It allows most molecules to pass freely, making it incorrect for selective permeability.
- **Cytoplasm**:
- The cytoplasm is a jelly-like substance within the cell that contains organelles. It does not exhibit selective permeability as it is not a membrane.
- **Protoplasm**:
- Protoplasm includes the cytoplasm and all organelles. Like the cytoplasm, it does not have selective permeability.

4. **Conclusion**:
- Based on the analysis, the only structure that exhibits selective permeability is the **cell membrane**. Therefore, the correct answer is **A) Cell membrane**.