The oxidation number of hyrogen is
(i) `0`
(ii) ` +1`
(iii) ` -1`
(iv) `+ 1` only.

Options

A. (i), (ii), (iii)
B. (i), (ii), (iii), (iv )
C. (i), (ii)
D. (i),(iii)

Explanation

To determine the oxidation number of hydrogen, let's analyze the different scenarios in which hydrogen can exist.

### Step-by-Step Solution:

1. **Understanding Oxidation Numbers**:
- The oxidation number (or oxidation state) of an element in a compound indicates the degree of oxidation (loss of electrons) of that element.

2. **Oxidation State in Elemental Form**:
- In its elemental form (e.g., H₂), hydrogen has an oxidation state of `0`. This is because there is no net charge when atoms are in their elemental state.

3. **Oxidation State in Compounds**:
- Hydrogen can have different oxidation states depending on the compounds it forms:
- When hydrogen is bonded to nonmetals (like in HCl), it typically has an oxidation state of `+1`. This is because it can lose its single electron.
- When hydrogen is bonded to metals (like in LiH or NaH), it can have an oxidation state of `-1`. This occurs because it can gain an electron from the metal.

4. **Summary of Oxidation States**:
- Therefore, the oxidation states of hydrogen can be summarized as:
- `0` in H₂ (elemental form)
- `+1` when bonded to nonmetals
- `-1` when bonded to metals

5. **Conclusion**:
- The oxidation number of hydrogen can be `0`, `+1`, or `-1` depending on the context. Hence, the correct answer to the question is that hydrogen can have oxidation states of `0`, `+1`, and `-1`.

### Final Answer:
- The oxidation number of hydrogen is (i) `0`, (ii) `+1`, and (iii) `-1`.