Which one the following is a covalent hydride ?

Options

A. `CaH_(2)`
B. NaH
C. `BH_(3)`
D. `BeH_(2)`

Explanation

To determine which of the given options is a covalent hydride, we need to analyze each option based on their bonding characteristics.

### Step-by-Step Solution:

1. **Understanding Hydrides**: Hydrides are compounds formed between hydrogen and another element. They can be classified into three types: ionic hydrides, covalent hydrides, and metallic (or interstitial) hydrides.

2. **Analyzing Option A: CAs2 (Calcium Sulfide)**:
- Calcium (Ca) is a metal, and sulfur (S) is a non-metal.
- The bond between Ca and S is ionic due to the transfer of electrons from the metal to the non-metal.
- Therefore, CAs2 is an ionic hydride.

3. **Analyzing Option B: NaH (Sodium Hydride)**:
- Sodium (Na) is a metal, and hydrogen (H) is a non-metal.
- The bond in NaH is also ionic, as sodium donates an electron to hydrogen.
- Thus, NaH is an ionic hydride.

4. **Analyzing Option C: B(S3) (Boron Sulfide)**:
- Boron (B) is a metalloid, and sulfur (S) is a non-metal.
- The bond between boron and sulfur involves sharing of electrons, which is characteristic of covalent bonding.
- Therefore, B(S3) is a covalent hydride.

5. **Analyzing Option D: BeH2 (Beryllium Hydride)**:
- Beryllium (Be) is a metal, and hydrogen (H) is a non-metal.
- BeH2 has a more complex bonding nature, but it is generally classified as an interstitial hydride rather than a covalent hydride.
- Thus, BeH2 is not a covalent hydride.

6. **Conclusion**: Among the options provided, only option C (B(S3)) is a covalent hydride.

### Final Answer:
The covalent hydride among the options is **C (B(S3))**.