Which of the following is an example of covalent bond ?

Options

A. Calcium oxide
B. Water
C. Ammonia
D. Sodium chloride

Explanation

To determine which of the following is an example of a covalent bond, we need to analyze the bonding nature of the compounds mentioned.

### Step-by-Step Solution:

1. **Identify the Compounds**: The question likely provides a list of compounds. For the sake of this solution, let's consider water (H₂O) and ammonia (NH₃) as examples of covalent bonds.

2. **Understanding Covalent Bonds**: A covalent bond is formed when two atoms share one or more pairs of electrons. This typically occurs between non-metal atoms.

3. **Analyzing Water (H₂O)**:
- Water consists of two hydrogen atoms and one oxygen atom.
- Oxygen has six valence electrons and needs two more to complete its octet.
- Each hydrogen atom has one electron and needs one more to complete its duet.
- In water, oxygen shares its electrons with the two hydrogen atoms, forming two covalent bonds. Thus, water is an example of a covalent bond.

4. **Analyzing Ammonia (NH₃)**:
- Ammonia consists of one nitrogen atom and three hydrogen atoms.
- Nitrogen has five valence electrons and needs three more to complete its octet.
- Each hydrogen atom shares its one electron with nitrogen.
- Nitrogen shares three of its electrons with the three hydrogen atoms, forming three covalent bonds. Therefore, ammonia is also an example of a covalent bond.

5. **Conclusion**: Based on the analysis, both water (H₂O) and ammonia (NH₃) are examples of covalent bonds. If the question provides multiple options, you would select these as correct answers.