Which of the following represents a pair of covalent hydrides?

Options

A. `CsH,AlH_(3)`
B. KH, NaH
C. `H_(2)S,HF`
D. `VH_(0.56),NH_(3)`

Explanation

To determine which of the given pairs represents covalent hydrides, we first need to understand the definitions of covalent hydrides, ionic hydrides, and metallic hydrides.

### Step-by-Step Solution:

1. **Understanding Covalent Hydrides**:
- Covalent hydrides are formed between non-metals and non-metals. They involve the sharing of electrons to form covalent bonds.

2. **Identifying the Given Compounds**:
- The compounds provided in the question are:
- CSH (Cesium Hydride)
- AlH3 (Aluminum Hydride)
- KH (Potassium Hydride)
- NaH (Sodium Hydride)
- H2S (Hydrogen Sulfide)
- HF (Hydrogen Fluoride)

3. **Analyzing Each Compound**:
- **CSH (Cesium Hydride)**:
- Cesium is an alkali metal (metal) and hydrogen is a non-metal. Therefore, this is an ionic hydride.
- **AlH3 (Aluminum Hydride)**:
- Aluminum is a metal and hydrogen is a non-metal. This is also considered an ionic hydride.
- **KH (Potassium Hydride)**:
- Potassium is another alkali metal, making this an ionic hydride as well.
- **NaH (Sodium Hydride)**:
- Sodium is a metal, thus this is also an ionic hydride.
- **H2S (Hydrogen Sulfide)**:
- Both hydrogen and sulfur are non-metals, so this is a covalent hydride.
- **HF (Hydrogen Fluoride)**:
- Both hydrogen and fluorine are non-metals, making this a covalent hydride as well.

4. **Conclusion**:
- The pairs that represent covalent hydrides are **H2S (Hydrogen Sulfide)** and **HF (Hydrogen Fluoride)**.

### Final Answer:
The pair of covalent hydrides is **H2S and HF**.