Assertion `(A) : ` Nuclear isomers have same atomic number and same mass number but with different radioactive properties.
Reason `(R) : U_((A))` and `U_((Z))` are nuclear isomers.

Answer

To solve the question regarding the assertion and reason about nuclear isomers, we can break it down into a step-by-step analysis:

### Step 1: Understand the Assertion
The assertion states that nuclear isomers have the same atomic number and mass number but exhibit different radioactive properties.

- **Atomic Number**: This is the number of protons in the nucleus of an atom, which defines the element.
- **Mass Number**: This is the total number of protons and neutrons in the nucleus.

**Conclusion**: The assertion is true because nuclear isomers indeed have the same atomic number and mass number but differ in their energy states and radioactive behavior.

### Step 2: Understand the Reason
The reason given is that Uranium A and Uranium Z are nuclear isomers.

- **Nuclear Isomers**: These are different states of the same nucleus that have the same number of protons and neutrons but differ in energy levels.
- **Uranium A and Uranium Z**: If these two isotopes are indeed nuclear isomers, they would have the same atomic and mass numbers but different energy states.

**Conclusion**: The reason is also true, as it correctly identifies Uranium A and Uranium Z as nuclear isomers.

### Step 3: Analyze the Relationship Between Assertion and Reason
Now, we need to determine if the reason provided is a correct explanation of the assertion.

- Since both the assertion and the reason are true, and the reason explains why nuclear isomers have different radioactive properties (due to differing energy levels), we can conclude that the reason supports the assertion.

### Final Conclusion
Both the assertion and reason are correct, and the reason is a valid explanation of the assertion. Therefore, the correct answer is that both statements are true and the reason is the correct explanation of the assertion.