Assertion: Euro II norms are framed to reduce the content of CO and aromatic compounds from fuels.
Reason: These compounds lead to reduced visibility and carboxyhemoglobin formation.

Options

A. If both Assertion and Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion and Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true but Reason is false, then mark (3).
D. If both Assertion and Reason are false, then mark (4).

Answer

To solve the question regarding the assertion and reason about Euro II norms, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
The assertion states that "Euro II norms are framed to reduce the content of CO (carbon monoxide) and aromatic compounds from fuels."

- **Evaluation**: Euro II norms are indeed designed to regulate emissions from vehicles, but they primarily focus on reducing sulfur content and aromatic hydrocarbons. The assertion incorrectly states that the norms aim to reduce carbon monoxide specifically.

### Step 2: Analyze the Reason
The reason states that "These compounds lead to reduced visibility and carboxyhemoglobin formation."

- **Evaluation**: Carbon monoxide does lead to the formation of carboxyhemoglobin, which can impair the blood's ability to carry oxygen. However, the assertion incorrectly links this to Euro II norms, which do not primarily target carbon monoxide. Additionally, while certain pollutants can affect visibility, the compounds mentioned in the assertion (sulfur and aromatic hydrocarbons) do not directly lead to reduced visibility in the same way carbon monoxide does.

### Step 3: Conclusion
Based on the evaluations:
- The assertion is false because Euro II norms focus on sulfur and aromatic compounds, not specifically on carbon monoxide.
- The reason is also false because it inaccurately describes the effects of the compounds targeted by Euro II norms.

Therefore, both the assertion and the reason are false.

### Final Answer
The correct option is **4**: Both assertion and reason are false.

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