Element X is a metal that forms salts with acidic oxides

Steps:

• Acidic oxides react with metals to produce metal salts via redox reactions.
• The described reaction (oxide + X → salts) matches metals reducing acidic oxides to form ionic salts of X.
• Metals like sodium react with CO2 (acidic oxide) to form Na2CO3.
• Metals conduct electricity due to mobile electrons.

Why A is correct:

• Metals conduct electricity as they have delocalized valence electrons that carry charge under an electric field.

Why the others are wrong:

• B: If X were a non-metal, its acidic oxide would not react with X to form salts; non-metals do not reduce their own oxides this way.
• C: Metal oxides are typically solid at room temperature and pressure, not gases.
• D: Metal oxides are ionic, not covalent.

Final answer: A