Assertion (A) : ABO blood group in human being is an example of multiple allelism.
Reason ( R): It has three alleles for the gene 1 i.e. `I_(A),I_(B),i`.

Options

A. Both assertion (A) and reason ( R) are true and reason ( R) is the correct explanation of assertion (A).
B. Both assertion (A) and reason ( R) are true but reason ( R) is not the correct explanation of assertion (A).
C. Assertion (A) is true but reason ( R) is false.
D. Assertion (A) is false but reason ( R) is true.

Explanation

To solve the question regarding the assertion and reason about ABO blood groups, we can follow these steps:

### Step 1: Understand the Assertion
The assertion states that "ABO blood group in human beings is an example of multiple allelism." Multiple allelism refers to the presence of more than two alleles for a genetic trait within a population. In the case of ABO blood groups, there are indeed three alleles: IA, IB, and i.

**Hint:** Recall the definition of multiple allelism and check if ABO blood groups fit this definition.

### Step 2: Analyze the Reason
The reason provided is that "It has three alleles for the gene 1 i.e. IA, IB, i." This statement is accurate as the ABO blood group system is determined by these three alleles. IA and IB are codominant, while i is recessive.

**Hint:** Verify if the number of alleles mentioned in the reason corresponds to the assertion about multiple allelism.

### Step 3: Determine the Relationship Between Assertion and Reason
Both the assertion and the reason are correct. The reason explains why the ABO blood group is an example of multiple allelism by identifying the three alleles involved.

**Hint:** Consider whether the reason logically supports the assertion. Does it provide a clear explanation?

### Step 4: Evaluate the Options
Based on the analysis:
1. Both the assertion and reason are correct, and the reason explains the assertion.
2. Both are correct, but the reason does not explain the assertion.
3. The assertion is correct, but the reason is wrong.
4. The assertion is wrong, but the reason is correct.

Since both the assertion and reason are correct and the reason explains the assertion, the correct option is the first one.

**Hint:** Review the options carefully to choose the one that matches your conclusion.

### Final Conclusion
The correct answer is that both the assertion and the reason are correct, and the reason explains the assertion.