Answer
Please see the work below.
Work Step by Step
We know that
a. Acidic, $NH_4NO_3$ is the salt of a weak base $NH_4O_H$ and a strong acid $HNO_3$.
b. Neutral $KNO_3$ is the salt of a strong base (KOH) and a strong acid $HNO_3$ so a solution of $NH_NO_3$ is neutral as none of the ions hudrolyze.
c. Acidic, as $Al(NO)_3$ is the salt of a weak base $[Al(OH)_3]$ and a strong acid $(HNO_3)$ so a solution of $Al(NO)$ is acidic due to the hydrolysis of $Al^{+3}$.
