Assertion : Agrobacterium tumefaciencs causes crown gall tumor in plants.
Reason : E.coli can't transfer DNA in plants.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A and R are false

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that "Agrobacterium tumefaciens causes crown gall tumor in plants."
- This statement is true. Agrobacterium tumefaciens is a well-known bacterium that induces crown gall tumors in plants by transferring a part of its DNA (T-DNA) into the plant cells, leading to uncontrolled growth.

2. **Understanding the Reason:**
- The reason states that "E. coli can't transfer DNA in plants."
- This statement is also true. Escherichia coli (E. coli) is a bacterium that does not have the capability to transfer DNA into plant cells like Agrobacterium tumefaciens does. E. coli is primarily a gut bacterium and does not have the mechanisms required for plant transformation.

3. **Evaluating the Relationship:**
- While both the assertion and the reason are true, the reason does not explain the assertion. The assertion is about Agrobacterium tumefaciens causing tumors in plants, while the reason discusses E. coli's inability to transfer DNA to plants. The two statements are related to different bacteria and their functions.

4. **Conclusion:**
- Since both the assertion and the reason are true, but the reason does not provide a correct explanation for the assertion, the correct answer is: "Both assertion and reason are true and reason is not the correct explanation of assertion."

### Final Answer:
Both assertion and reason are true and reason is not the correct explanation of assertion.