Assertion `(A) :` In radioactive disintegrations, `._(2)H^(4)` nuclei can come out of the nucleus but lighter `._(2)H^(3)` cannot.
Reason `(R) :` The binding energy of `._(2)H^(3)` is more than that of `._(2)H^(4)`.

Options

A. If both `(A)` and `(R)` are correct , and `(R)` is the correct explanation of `(A)`
B. If both `(A)` and `(R)` are correct, but (R) is not the correct explanation of `(A)`
C. If `(A)` is correct, but `(R)` is incorrect.
D. If `(A)` is incorrect, but `(R)` is correct.

Explanation

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

### Step 1: Understanding the Assertion
The assertion states that in radioactive disintegrations, helium nuclei (specifically, \( _{2}^{4}\text{He} \)) can come out of the nucleus, while lighter tritium nuclei (specifically, \( _{1}^{3}\text{H} \)) cannot.

**Hint:** Consider the stability of the nuclei involved and how they relate to radioactive decay.

### Step 2: Analyzing the Stability of Nuclei
In radioactive disintegration, unstable nuclei tend to decay into more stable forms. Helium-4 (\( _{2}^{4}\text{He} \)) is a more stable nucleus compared to tritium (\( _{1}^{3}\text{H} \)). This means that when a nucleus undergoes radioactive decay, it is more likely to emit a helium nucleus because it leads to a more stable configuration.

**Hint:** Think about the concept of stability in nuclear chemistry and how it influences the decay process.

### Step 3: Understanding the Reason
The reason states that the binding energy of tritium is more than that of helium. However, this statement is incorrect. The binding energy of a nucleus is an indicator of its stability; a higher binding energy means a more stable nucleus. Helium-4 has a higher binding energy than tritium, which means it is more stable.

**Hint:** Recall the relationship between binding energy and nuclear stability.

### Step 4: Conclusion
Based on the analysis:
- The assertion is correct: Helium nuclei can come out of the nucleus during radioactive decay because they are more stable.
- The reason is incorrect: The binding energy of tritium is not greater than that of helium; in fact, helium has a higher binding energy.

Thus, the final conclusion is:
- Assertion (A) is true.
- Reason (R) is false.

### Final Answer:
Assertion (A) is correct, and Reason (R) is incorrect.