Which of the following salts undergoes hydrolysis?

The percentage degree of hydrolysis of a salt of weak acid $(HA)$ and weak base $(BOH)$ in its $0.1 \ M$ solution is found to be $10 \%$. If the molarity of the solution is $0.05 \ M$,the percentage hydrolysis of the salt should be ....... $\%$.

$20\,mL$ of $0.1\,M\,NH_{4}OH$ is mixed with $40\,mL$ of $0.05\,M\,HCl$. The $pH$ of the mixture is nearest to. (Given: $K_{b}(NH_{4}OH) = 1 \times 10^{-5}, \log 2 = 0.30, \log 3 = 0.48, \log 5 = 0.69, \log 7 = 0.84, \log 11 = 1.04$) (in $.2$)

$NH_4CN$ is a salt of a weak acid $HCN$ $(K_a = 6.2 \times 10^{-10})$ and a weak base $NH_4OH$ $(K_b = 1.8 \times 10^{-5})$. $A$ $1 \ M$ solution of $NH_4CN$ will be:

The aqueous solution of $CuSO_4$ is

Which of the following has the lowest degree of hydrolysis?