To determine the correct order of N-compounds in decreasing order of oxidation states, we need to calculate the oxidation state of nitrogen in each compound.$\\$1. $$HNO$_3: \\$• Let the oxidation state of $N$ be $x. \\$• The oxidation state of $H$ is $+1$ and $O$ is $-2. \\$• The equation is: $+1 + x + 3(-2) = 0 \\ x - 5 = 0 \\ x = +5 \\$2. $$NO$: \\$• Let the oxidation state of $N$ be $x. \\$• The oxidation state of $O$ is $-2. \\$• The equation is: $x + (-2) = 0 \\ x = +2 \\$3. $$N$_2: \\$• Since it is a diatomic molecule, the oxidation state of $N$ is $0. \\$4. $$NH$_4$Cl$: \\$• Let the oxidation state of $N$ be $x. \\$• The oxidation state of $H$ is $+1$ and $Cl$ is $-1. \\$• The equation is: $x + 4(+1) + (-1) = 0 \\ x + 4 - 1 = 0 \\ x = -3 \\$Now, arrange the compounds in decreasing order of oxidation states:$\\$HNO$_3 (+5),$NO$(+2),$N$_2 (0),$NH$_4$Cl$(-3) \\$Therefore, the correct order is:$\\$HNO$_3,$NO$,$N$_2,$NH$_4$Cl$\\$This corresponds to Option 3.