Assertion : Benign tumours are called neoplastic cells.
Reason : Malignant tumour remain in place to form a compact mass by a process known as metastasis.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertin is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Benign tumors are called neoplastic cells."
- **Definition**: Benign tumors are non-cancerous growths that do not invade surrounding tissues or spread to other parts of the body. They are indeed made up of neoplastic cells, but the term "neoplastic" generally refers to any tumor cells, including malignant ones. Therefore, while benign tumors consist of neoplastic cells, they are not typically referred to as such in the same context as malignant tumors.

2. **Evaluating the Reason**:
- The reason states that "Malignant tumors remain in place to form a compact mass by a process known as metastasis."
- **Definition**: Malignant tumors are cancerous and characterized by their ability to invade surrounding tissues and spread (metastasize) to distant sites in the body. The statement incorrectly describes malignant tumors as remaining in place; instead, they spread to other locations through the bloodstream or lymphatic system.

3. **Conclusion**:
- Since the assertion is incorrect (benign tumors are not simply called neoplastic cells in the same context) and the reason is also incorrect (malignant tumors do not remain in place), we conclude that both the assertion and the reason are false.

4. **Final Answer**:
- Therefore, the correct option is that both the assertion and the reason are false.