A:1,3-butadiene is the monomer for natural rubber.
R: Natural rubber is formed through anionic addition polymerisation.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark 1.
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark 2.
C. If Assertion is true statement but Reason is false, then mark 3.
D. If both Assertion and Reason are false statements the mark 4.

Answer

To solve the question regarding the assertion and reasoning about natural rubber and its monomer, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
**Assertion (A):** 1,3-butadiene is the monomer for natural rubber.

- **Explanation:** Natural rubber is primarily composed of polyisoprene, which is derived from isoprene. Isoprene (2-methyl-1,3-butadiene) is actually a derivative of 1,3-butadiene, but it is not correct to say that 1,3-butadiene itself is the monomer for natural rubber. Therefore, this assertion is **incorrect**.

### Step 2: Analyze the Reason
**Reason (R):** Natural rubber is formed through anionic addition polymerization.

- **Explanation:** Natural rubber is indeed formed through the polymerization of isoprene, and this process can involve anionic polymerization. Anionic polymerization is a method where a negatively charged ion initiates the polymerization process. However, the statement does not accurately reflect the process of natural rubber formation as it does not specify that isoprene is the actual monomer used. Therefore, this reason is also **incorrect**.

### Step 3: Conclusion
Both the assertion and the reason are incorrect. Therefore, the correct answer to the question is that both the assertion and the reason are wrong.

### Final Answer:
Both the assertion (A) and the reason (R) are incorrect.

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