Assertion (A) : Antiferromagnetic substances on heating to high temperature become paramagnetic.
Reason (R ) : On heating, the randomization of spins occurs.

Options

A. If both the statement are TRUE and STATEMENT -2 is the correct explanation of STATEMENT -1
B. If both the statement are TRUE and STATEMENT -2 is NOT the correct explanation of STATEMENT -1
C. If STATEMENT -1 is the correcct and TRUE and STATEMENT -2 is FALSE
D. If STATEMENT -1 is the correcct and FALSE and STATEMENT -2 is TRUE

Answer

### Step-by-Step Solution:

1. **Understanding Antiferromagnetic Substances**:
- Antiferromagnetic substances are materials where the magnetic moments of atoms or ions align in opposite directions (anti-parallel) in equal numbers. This results in a net magnetic moment of zero because the opposing moments cancel each other out.

2. **Effect of Heating on Antiferromagnetic Substances**:
- When antiferromagnetic substances are heated to high temperatures, the thermal energy causes the alignment of these magnetic moments to become disordered or randomized.

3. **Transition to Paramagnetism**:
- As the spins become randomized due to heating, the cancellation of the magnetic moments is disrupted. This results in a net magnetic moment, which is characteristic of paramagnetic substances. Paramagnetic materials have unpaired electrons and exhibit a net magnetic moment.

4. **Conclusion on Assertion and Reason**:
- The assertion states that antiferromagnetic substances become paramagnetic upon heating, which is correct. The reason provided states that this is due to the randomization of spins, which correctly explains why the transition occurs.

5. **Final Evaluation**:
- Both the assertion and the reason are true, and the reason is indeed the correct explanation for the assertion.

### Final Answer:
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

---