1. Identify the target transformation

We need to convert propan-1-ol to n-butylamine.

• Propan-1-ol: $CH_3CH_2CH_2OH$
• n-Butylamine: $CH_3CH_2CH_2CH_2NH_2$

Notice that the product has one extra carbon atom compared to the starting alcohol.

2. Plan the carbon chain extension

To increase the carbon chain by one carbon, a standard method is:

• Convert alcohol to alkyl halide
• React with $KCN$ to form nitrile
• Reduce nitrile to primary amine

This works because the cyanide carbon becomes part of the chain.

3. Step 1: Convert propan-1-ol to alkyl halide

Using $SOCl_2$:

$CH_3CH_2CH_2OH \xrightarrow{SOCl_2} CH_3CH_2CH_2Cl$

So propan-1-ol becomes 1-chloropropane.

4. Step 2: Chain extension using $KCN$

Alkyl chloride undergoes nucleophilic substitution with $KCN$:

$CH_3CH_2CH_2Cl \xrightarrow{KCN} CH_3CH_2CH_2CN$

This gives butanenitrile.

Now the chain has increased from 3 carbons to 4 carbons.

5. Step 3: Reduce nitrile to primary amine

Reduction of nitrile gives primary amine:

$CH_3CH_2CH_2CN \xrightarrow{H_2/Ni\;\text{or}\;Na(Hg)/C_2H_5OH} CH_3CH_2CH_2CH_2NH_2$

This is n-butylamine.

6. Check the options

Option A

(i) $SOCl_2$
(ii) $KCN$
(iii) $H_2/Ni$, $Na(Hg)/C_2H_5OH$

This exactly matches the required sequence.

✅ Correct

Option B

(i) $HCl$
(ii) $H_2/Ni$, $Na(Hg)/C_2H_5OH$

This converts alcohol to chloride, but there is no chain extension step using $KCN$. So it cannot produce n-butylamine.

❌ Incorrect

Option C

(i) $SOCl_2$
(ii) $KCN$
(iii) $CH_3NH_2$

After forming nitrile, reaction with $CH_3NH_2$ will not give n-butylamine.

❌ Incorrect

Option D

(i) $HCl$
(ii) $CH_3NH_2$

No proper carbon chain extension and not a valid route to n-butylamine.

❌ Incorrect

7. Final answer

The correct sequential order of reagents is:

$\boxed{\text{A}}$

This agrees with the stored correct answer.