Boron can be obtained by:

Options

A. reduction of `B_(2)O_(3)` by `C`.
B. reduction of `BCl_(3)` with `H_(2)` at `1270k`.
C. thermal decomposition of boron halides at `1173 k`.
D. electrolytic reduction of `KBF_(4)` in `KF` at `1073 k`.

Explanation

To determine how boron can be obtained, we need to analyze the different methods mentioned in the question. Let's break down the options step by step:

### Step 1: Reduction of B2O3 by Carbon
- **Analysis**: The first method mentioned is the reduction of B2O3 (boron trioxide) by carbon (C). However, this method is not correct for obtaining boron.
- **Conclusion**: This method does not yield boron.

### Step 2: Reduction of BCl3 with H2
- **Reaction**: The second method is the reduction of BCl3 (boron trichloride) with hydrogen (H2) at a high temperature of 1270 K. The reaction can be represented as:
\[ \text{BCl}_3 + \text{H}_2 \rightarrow \text{B} + 3\text{HCl} \]
- **Conclusion**: This method is correct and does produce boron.

### Step 3: Thermal Decomposition of Boron Halide
- **Reaction**: The third method involves the thermal decomposition of a boron halide (BX3) at 1173 K. The general reaction can be written as:
\[ \text{BX}_3 \rightarrow \text{B} + \frac{3}{2}\text{X}_2 \]
- **Conclusion**: This method is also correct and yields boron.

### Step 4: Electrolytic Reduction of KBF4
- **Reaction**: The fourth method is the electrolytic reduction of potassium tetrafluoroborate (KBF4) in potassium fluoride (KF) at 1073 K. The reaction can be represented as:
\[ \text{KBF}_4 \rightarrow \text{K}^+ + \text{BF}_4^- \]
At the anode, the BF4- ion can be reduced to form boron:
\[ \text{BF}_4^- + 4\text{e}^- \rightarrow \text{B} + 2\text{F}_2 \]
- **Conclusion**: This method is correct and produces boron.

### Final Conclusion
Based on the analysis:
- The methods that can produce boron are:
- B: Reduction of BCl3 with H2
- C: Thermal decomposition of boron halide
- D: Electrolytic reduction of KBF4

Thus, the correct answers are **B, C, and D**.

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