The regulation of the flow of material into and outside the cell depends on:

Options

A. cell membrane
B. mechanism of osmosis
C. chemical composition of plasma membrane
D. plasma membrane's permeability

Explanation

To answer the question "The regulation of the flow of material into and outside the cell depends on:", we can follow these steps:

### Step 1: Understand the Role of the Cell Membrane
The cell membrane, also known as the plasma membrane, is a crucial structure that surrounds the cell. It acts as a barrier that separates the interior of the cell from the external environment.

**Hint:** Think about what the cell membrane does in terms of protection and separation.

### Step 2: Define Semi-permeability
The plasma membrane is described as semi-permeable or selectively permeable. This means that it allows certain substances to pass through while blocking others. This selectivity is essential for maintaining the internal environment of the cell.

**Hint:** Consider what "selectively permeable" means in terms of substance movement.

### Step 3: Identify Factors Affecting Material Flow
The flow of materials into and out of the cell is influenced by the permeability of the plasma membrane. This permeability determines which substances can enter or exit the cell and is influenced by various factors, including the size, charge, and polarity of the molecules.

**Hint:** Reflect on how different substances interact with the membrane.

### Step 4: Evaluate the Options
Now, let's evaluate the provided options:
1. Cell membrane - While it is involved, it is too general.
2. Mechanism of osmosis - This is a process but does not solely regulate flow.
3. Chemical composition of plasma membrane - This affects permeability but is not the direct regulator.
4. Plasma membrane's permeability - This is the correct answer as it directly relates to the regulation of material flow.

**Hint:** Compare each option to see which one directly relates to the control of material movement.

### Conclusion
The regulation of the flow of material into and outside the cell depends on the **plasma membrane's permeability**.

**Final Answer:** Plasma membrane's permeability.