Assertion: lonising radiations are harmful for the living organisms.
Reason: They form toxic photo products in the cells.

Options

A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
B. If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.
C. If Assertion is true but the Reason is false.
D. If both Assertion and Reasom are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Ionizing radiations are harmful for living organisms." This is true because ionizing radiation, which includes ultraviolet rays, gamma rays, and X-rays, can cause significant damage to biological tissues.

**Hint**: Consider the types of ionizing radiation and their effects on living cells.

2. **Understanding the Reason**:
- The reason provided is "They form toxic photo products in the cells." This statement is false. Ionizing radiation does not primarily form toxic photo products; instead, it causes mutations in DNA by altering the nucleotide sequences.

**Hint**: Think about how ionizing radiation interacts with DNA and the types of damage it can cause.

3. **Evaluating the Relationship**:
- The assertion is true, but the reason is false. Therefore, the reason does not correctly explain the assertion.

**Hint**: Analyze whether the reason supports or contradicts the assertion.

4. **Conclusion**:
- Based on the evaluation, the correct answer is that the assertion is true, but the reason is false. This leads us to select the option that states "Assertion true, reason false."

**Hint**: Look for answer choices that differentiate between the truth of the assertion and the reason.

### Final Answer:
- The correct option is: **Assertion true, reason false.**