What is meant by contact inhibition ?

Options

A. Contact with other cells promote their uncontrolled growth .
B. Contact with other cells doesn’t inhibits their uncontrolled growth.
C. Contact with other cells inhibits their programmed cell death.
D. Contact with other cells inhibits their uncontrolled growth

Answer

### Step-by-Step Solution:

1. **Understanding Contact Inhibition**:
- Contact inhibition is a biological process that regulates cell growth and division. It occurs when cells come into contact with each other, which signals them to stop dividing.

2. **Analyzing the Options**:
- **Option 1**: "Contact with other cells promote their uncontrolled growth."
- This option is incorrect because contact with other cells does not promote growth; it inhibits it.
- **Option 2**: "Contact with other cells does not inhibit uncontrolled growth."
- This option is also incorrect as it suggests that contact does not have an effect, which contradicts the definition of contact inhibition.
- **Option 3**: "Contact with other cells inhibit their programmed cell death."
- This option is incorrect because contact inhibition is related to growth regulation, not programmed cell death (apoptosis).
- **Option 4**: "Contact with other cells inhibit their uncontrolled growth."
- This option is correct as it accurately describes contact inhibition, where the presence of neighboring cells leads to the cessation of cell division.

3. **Conclusion**:
- Based on the analysis of the options, the correct answer is **Option 4**: "Contact with other cells inhibit their uncontrolled growth."