Number of `S-S` linkage in Marshall acid `=a`
Number of `P-P` linkage in Pyrophosphoric acid `=b`
Number of `O-O` linkage in Caro acid `=c`
Number of `C=C` lilnkage in Carbon suboxide `=d`
Find out the value of `a+b+c+d`?

Explanation

To solve the problem, we need to analyze the compounds mentioned and determine the number of specific linkages in each. Let's break it down step by step.

### Step 1: Determine the number of `S-S` linkages in Marshall acid (`a`)

1. **Identify the structure of Marshall acid**: Marshall acid is represented as HOSO2H (or similar variations).
2. **Count the `S-S` linkages**: In the structure of Marshall acid, there are no sulfur-sulfur (S-S) linkages present.
3. **Conclusion**: Therefore, the value of `a = 0`.

### Step 2: Determine the number of `P-P` linkages in Pyrophosphoric acid (`b`)

1. **Identify the structure of Pyrophosphoric acid**: The structure can be represented as H2P2O7.
2. **Count the `P-P` linkages**: In this structure, there are no direct phosphorus-phosphorus (P-P) linkages.
3. **Conclusion**: Therefore, the value of `b = 0`.

### Step 3: Determine the number of `O-O` linkages in Caro acid (`c`)

1. **Identify the structure of Caro acid**: Caro acid can be represented as H2SO5.
2. **Count the `O-O` linkages**: In the structure of Caro acid, there is one direct oxygen-oxygen (O-O) linkage.
3. **Conclusion**: Therefore, the value of `c = 1`.

### Step 4: Determine the number of `C=C` linkages in Carbon suboxide (`d`)

1. **Identify the structure of Carbon suboxide**: Carbon suboxide has the structure O=C=C=O.
2. **Count the `C=C` linkages**: In this structure, there are two direct carbon-carbon (C=C) double bond linkages.
3. **Conclusion**: Therefore, the value of `d = 2`.

### Step 5: Calculate the total `a + b + c + d`

Now that we have determined the values:
- `a = 0`
- `b = 0`
- `c = 1`
- `d = 2`

We can calculate:
\[ a + b + c + d = 0 + 0 + 1 + 2 = 3 \]

### Final Answer:
The value of \( a + b + c + d = 3 \).

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