Which of the following aqueous solutions will have a $pH$ less than $7.0$?

The $pH$ is less than $7$ for the solution of:

Calculate the percentage of hydrolysis in $0.01 \ M$ aqueous solution of $NaOCN$ ($K_b$ for $OCN^{-} = 10^{-10}$)

The $K_{a}$ for $CH_{3}COOH$ is $1.8 \times 10^{-5}$ and $K_{b}$ for $NH_{4}OH$ is $1.8 \times 10^{-5}$. The $pH$ of ammonium acetate solution will be

The number of hydroxide ions,produced by one molecule of sodium carbonate $(Na_2CO_3)$ on hydrolysis is

The $pH$ of a $NaCl$ solution is: