Water enters a cell due to

Options

A. OP
B. DPD
C. TP
D. WP

Explanation

### Step-by-Step Solution:

1. **Understanding Water Movement in Cells**: Water enters a cell primarily due to osmotic pressure, which is the pressure that develops when a solution is separated from pure solvent by a semi-permeable membrane.

2. **Defining Osmotic Pressure (OP)**: Osmotic pressure (OP) is represented by the symbol ?S. It is the potential pressure that drives water from an area of lower solute concentration (pure solvent) to an area of higher solute concentration (solution).

3. **Concept of Osmotically Active Solution**: An osmotically active solution is one that has solute particles and can attract water. Water moves from the pure solvent side to the solution side because of the osmotic pressure.

4. **Understanding Diffusion Pressure Deficit (DPD)**: DPD, represented as ?w, is the reduction in the diffusion pressure of water due to the presence of solute particles. The DPD is calculated as OP - DP (where DP is the diffusion pressure of the pure solvent).

5. **Water Movement and DPD**: Water will move from a solution with lower DPD to a solution with higher DPD. This movement is essential for the entry of water into cells.

6. **Turgor Pressure (TP)**: Turgor pressure is the hydrostatic pressure that develops within a cell due to the osmotic entry of water. It occurs in confined systems (like plant cells) and is the pressure exerted by the fluid against the cell wall.

7. **Wall Pressure (WP)**: Wall pressure is the force exerted by the cell wall against the turgor pressure. It acts in the opposite direction to turgor pressure.

8. **Conclusion**: The correct answer to the question "Water enters a cell due to" is **Diffusion Pressure Deficit (DPD)**, as it is the driving force for water movement into cells.

### Final Answer:
Water enters a cell due to **Diffusion Pressure Deficit (DPD)**.

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