Which of the following hydrogen halides has the most polar bond ?
(i) `HF" "(ii)HCl`
(iii) `HBr" "(iv) HI.`

Explanation

To determine which hydrogen halide has the most polar bond among HF, HCl, HBr, and HI, we need to analyze the electronegativity of the halogens involved and how it affects the polarity of the bond with hydrogen.

### Step-by-Step Solution:

1. **Understanding Polarity**: A polar bond occurs when there is a significant difference in electronegativity between the two atoms involved in the bond. The atom with higher electronegativity attracts the shared electrons more strongly, creating a dipole moment.

2. **Electronegativity Values**: The electronegativity values for the relevant elements are:
- Fluorine (F): 4.0
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