Which of the following lanthanide is commonly used?

Options

A. Lanthanum
B. Nobelium
C. Thorium
D. Cerium

Explanation

To determine which lanthanide is commonly used, we will analyze the options provided: lanthanum, nobelium, thorium, and cerium.

### Step-by-Step Solution:

1. **Identify the Options**:
- The lanthanides listed are:
- Lanthanum (La)
- Nobelium (No)
- Thorium (Th)
- Cerium (Ce)

2. **Understand the Lanthanides**:
- Lanthanides are a series of 15 metallic elements from lanthanum (atomic number 57) to lutetium (atomic number 71). They are known for their similar properties and are often used in various applications.

3. **Research Common Uses**:
- **Lanthanum**: Used in camera and telescope lenses, and in some types of batteries.
- **Nobelium**: A synthetic element with limited applications, primarily in research.
- **Thorium**: Used in nuclear reactors and as a potential fuel source.
- **Cerium**: Widely used in catalysts, glass polishing, and as an additive in various materials.

4. **Identify the Most Commonly Used Lanthanide**:
- Among the options, cerium is the most commonly used lanthanide due to its applications in various industries, particularly in catalysts and glass manufacturing.

5. **Conclusion**:
- The correct answer is **Cerium (Ce)**, as it is the most commonly used lanthanide.

### Final Answer:
**Cerium (Ce)** is the most commonly used lanthanide.