An aqueous solution of X is added slowly to an aqueous solution of Y as shown in List-I. The variation in conductivity of these reactions is given in List-II. Match List-I with List-II and select the correct answer using the code given below the lists:
`{:(List-I,List-II),((P)(C_(2)H_(5))_(3)N +CH_(3)COOH,(1)"Conductivity decreases adn then increases"),(" X Y",),((Q)KI(0.1M)+AgNO_(3)(0.01M),(2)"Conductivity decreases and then does not change much"),(" X Y",),((R)CH_(3)COOH+KOH,(3)"Conductivity increases and then does not change much"),(" X Y",),((S)NaOH+Hi,(4)"Conductivity does not change much and then increases"),(" X Y",):}`
Codes:

Options

A. `{:(P,Q,R,S),(3,4,2,1):}`
B. `{:(P,Q,R,S),(4,3,2,1):}`
C. `{:(P,Q,R,S),(2,3,4,1):}`
D. `{:(P,Q,R,S),(1,4,3,2):}`

Explanation

To solve the problem, we need to analyze the reactions and their effects on conductivity step by step.

### Step-by-Step Solution:

1. **Identify the Reactions**:
- **P**: \( (C_2H_5)_3N + CH_3COOH \)
- **Q**: \( KI(0.1M) + AgNO_3(0.01M) \)
- **R**: \( CH_3COOH + KOH \)
- **S**: \( NaOH + HI \)

2. **Analyze Reaction P**:
- **Type**: Weak base (triethylamine) + weak acid (acetic acid).
- **Conductivity**: Initially increases as ions are formed, but then levels off as the reaction reaches equilibrium.
- **Match**: This corresponds to (3) "Conductivity increases and then does not change much".

3. **Analyze Reaction Q**:
- **Type**: Strong electrolyte (KI) + strong electrolyte (AgNO3).
- **Conductivity**: The conductivity does not change much initially as both are strong electrolytes, but then it increases as AgI precipitates out.
- **Match**: This corresponds to (4) "Conductivity does not change much and then increases".

4. **Analyze Reaction R**:
- **Type**: Weak acid (acetic acid) + strong base (KOH).
- **Conductivity**: Initially decreases as the weak acid reacts with the strong base, but then levels off as the solution becomes neutralized.
- **Match**: This corresponds to (2) "Conductivity decreases and then does not change much".

5. **Analyze Reaction S**:
- **Type**: Strong base (NaOH) + strong acid (HI).
- **Conductivity**: Initially decreases as the acid and base neutralize each other, but then increases as the solution becomes more ionic.
- **Match**: This corresponds to (1) "Conductivity decreases and then increases".

### Final Matching:
- **P** matches with (3)
- **Q** matches with (4)
- **R** matches with (2)
- **S** matches with (1)

### Conclusion:
The correct answer code is:
- P - 3
- Q - 4
- R - 2
- S - 1