The correct answer is option 1, carbon dioxide.
When carbon dioxide dissolves in water, it forms carbonic acid. This happens because carbon dioxide reacts with water to produce carbonic acid, which is a weak acid. The equation for this reaction is: CO2 + H2O [REPLACEMENT] H2CO3.
Carbonic acid releases hydrogen ions (H+) when it dissociates in water, making the solution acidic. The presence of hydrogen ions gives the solution a sour taste and allows it to conduct electricity.
Option 2, oxygen, does not dissolve to form an acidic solution. It is a non-reactive gas and does not undergo significant chemical reactions with water.
Option 3, nitrogen, also does not dissolve in water to form an acidic solution. Nitrogen is an inert gas and does not react with water.
Option 4, hydrogen, can dissolve in water to form a solution, but it does not give an acidic solution. Hydrogen gas dissolves to form a neutral solution.
Therefore, the correct answer is option 1, carbon dioxide, as it dissolves in water to give an acidic solution.