Magnesium oxide can be obtained by heating :-

Options

A. `MgCO_(3)`
B. `Mg(NO_(3))_(2)`
C. `Mg(OH)_(2)`
D. All

Answer

To determine how magnesium oxide (MgO) can be obtained by heating, we can analyze the given compounds one by one.

### Step-by-Step Solution:

1. **Understanding the Compounds**:
We need to evaluate the options provided (A, B, C, D) which likely represent different magnesium compounds. Common compounds to consider include magnesium carbonate (MgCO3), magnesium nitrate (Mg(NO3)2), and magnesium hydroxide (Mg(OH)2).

2. **Heating Magnesium Carbonate (MgCO3)**:
- When magnesium carbonate is heated, it decomposes to form magnesium oxide and carbon dioxide:
\[ \text{MgCO}_3 \rightarrow \text{MgO} + \text{CO}_2 \]
- This reaction indicates that MgCO3 can produce MgO upon heating.

3. **Heating Magnesium Nitrate (Mg(NO3)2)**:
- When magnesium nitrate is heated, it decomposes to form magnesium oxide, nitrogen dioxide, and oxygen:
\[ 2 \text{Mg(NO}_3)_2 \rightarrow 2 \text{MgO} + 4 \text{NO}_2 + \text{O}_2 \]
- This shows that Mg(NO3)2 also produces MgO upon heating.

4. **Heating Magnesium Hydroxide (Mg(OH)2)**:
- When magnesium hydroxide is heated, it decomposes to form magnesium oxide and water:
\[ \text{Mg(OH)}_2 \rightarrow \text{MgO} + \text{H}_2\text{O} \]
- This indicates that Mg(OH)2 can also yield MgO when heated.

5. **Conclusion**:
- Since all three compounds (MgCO3, Mg(NO3)2, and Mg(OH)2) can produce magnesium oxide upon heating, we conclude that the correct answer is that magnesium oxide can be obtained by heating any of the compounds mentioned.

### Final Answer:
All of the above compounds (MgCO3, Mg(NO3)2, Mg(OH)2) can be heated to obtain magnesium oxide (MgO).