Assersion : Out of three meansurements `l = 0.7 m, l = 0.70m` and `l = 0.700m` the last one is most accurate.
Reason: In every meansurements only the last significant digit is not accurately known.

Options

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

Answer

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

### Step 1: Understand the Assertion
The assertion states that out of the three measurements \( l = 0.7 \, m \), \( l = 0.70 \, m \), and \( l = 0.700 \, m \), the last one is the most accurate.

### Step 2: Analyze the Measurements
- **Measurement 1**: \( l = 0.7 \, m \) has **1 significant digit**.
- **Measurement 2**: \( l = 0.70 \, m \) has **2 significant digits**.
- **Measurement 3**: \( l = 0.700 \, m \) has **3 significant digits**.

### Step 3: Determine Accuracy
In terms of accuracy, the more significant digits a measurement has, the more precise it is. Therefore, the measurement with the most significant digits (in this case, \( l = 0.700 \, m \)) is indeed the most accurate.

### Step 4: Understand the Reason
The reason provided states that in every measurement, only the last significant digit is not accurately known. This statement is misleading because the last significant digit in \( 0.700 \, m \) is indeed accurately known.

### Step 5: Conclusion
- The assertion is **true** because \( l = 0.700 \, m \) is the most accurate measurement due to having the most significant digits.
- The reason is **false** because it incorrectly states that the last significant digit is not accurately known.

### Final Answer
The correct conclusion is that the assertion is true, but the reason is false. Thus, the correct option is that the assertion is true but the reason is false.

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