Calculate number of sigma `(sigma)` and pi` (pi)` bonds in the above structures (i-iv).

Explanation

To calculate the number of sigma (σ) and pi (π) bonds in the given structures (i-iv), we will analyze each structure step by step.

### Structure i:
1. **Identify Pi Bonds**:
- The structure has 2 double bonds.
- Each double bond consists of 1 σ bond and 1 π bond.
- Therefore, the number of π bonds = 2.

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