What happens when metal oxide reacts with water?

Which of the following is a weak acid?

According to the Bronsted-Lowry acid-base theory,the substance which donates a proton $(H^+)$ to another substance is called ............

What will be the action of the following substances on litmus paper? Dry $HCl$ gas,Moistened $NH_3$ gas,Lemon juice,Carbonated soft drink,Curd,Soap solution.

Acids do not show acidic behaviour in the absence of water but do so in water. Justify this statement with the help of a chemical equation.

$(a)$ Give the chemical names of acids present in:
$(i)$ ants
$(ii)$ lemon
$(iii)$ milk
$(iv)$ tomato