A : Silicon is insulator at 0 K but semiconductor at room temperature.
R : Conductivity of silicon at room temperature is due to electronic defect.

Options

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

Answer

To analyze the given statements about silicon, we will break down the assertion and reason step by step.

### Step 1: Understand the Assertion
**Assertion (A):** Silicon is an insulator at 0 K but a semiconductor at room temperature.

- At 0 K (absolute zero), silicon has no thermal energy, meaning that its electrons are in their lowest energy state and cannot move. Therefore, silicon behaves as an insulator at this temperature.
- At room temperature, silicon gains thermal energy, allowing some electrons to move from the valence band to the conduction band. This movement of electrons enables silicon to conduct electricity, classifying it as a semiconductor.

### Step 2: Understand the Reason
**Reason (R):** The conductivity of silicon at room temperature is due to electronic defects.

- The conductivity of silicon at room temperature is indeed influenced by the presence of defects, such as vacancies or impurities, which can create energy levels within the band gap.
- These defects can provide additional energy states that allow electrons to be thermally excited into the conduction band, contributing to the semiconductor behavior of silicon.

### Step 3: Evaluate the Truth of Both Statements
- Both the assertion and the reason are true.
- The assertion correctly describes the behavior of silicon at different temperatures, and the reason accurately explains the mechanism behind the conductivity of silicon at room temperature.

### Step 4: Determine the Relationship Between Assertion and Reason
- The reason provides a correct explanation for the assertion. The conductivity of silicon at room temperature is indeed due to the electronic defects that allow electrons to move and contribute to conduction.

### Conclusion
Since both the assertion and the reason are true, and the reason correctly explains the assertion, the correct answer is:

**Answer:** Both Assertion and Reason are true, and the Reason is the correct explanation of the Assertion.