All carboxylic acids are characterized by a reaction with: 1) aldehydes 2) salts of strong mineral acids

All carboxylic acids are characterized by a reaction with: 1) aldehydes 2) salts of strong mineral acids 3) oxides of non-metals 4) alkalis

All carboxylic acids exhibit typical acidic properties. They can interact with metals, their oxides or their basic hydroxides. As a result, salts of the corresponding metals are formed. Also, carboxylic acids can displace a weaker acid from its salt, while at the same time they themselves can be displaced by a stronger acid.
Therefore, the correct answer is: 4) alkalis.