The smallest and largest units of length are.

Options

A. Millimeter and Centimeter
B. Fermi and Parsec
C. Millimeter and Kilometer
D. Millimeter and Light Year

Answer

To determine the smallest and largest units of length, we need to consider various units of measurement in the metric system and beyond.

### Step-by-Step Solution:

1. **Identify Smallest Units of Length**:
- The smallest commonly used unit of length is the **Fermi** (fm), which is equal to \(10^{-15}\) meters.
- Other small units include the **picometer** (pm) which is \(10^{-12}\) meters, and the **nanometer** (nm) which is \(10^{-9}\) meters.

2. **Identify Largest Units of Length**:
- The largest commonly used unit of length is the **parsec** (pc), which is used in astronomy. One parsec is approximately equal to \(3.26\) light-years or about \(3.09 \times 10^{16}\) meters.
- Other large units include the **light-year**, which is the distance light travels in one year, and the **astronomical unit** (AU), which is the average distance from the Earth to the Sun.

3. **Conclusion**:
- Therefore, the smallest unit of length is the **Fermi** (\(10^{-15}\) meters), and the largest unit of length is the **parsec**.

### Final Answer:
- **Smallest Unit of Length**: Fermi (\(10^{-15}\) meters)
- **Largest Unit of Length**: Parsec (approximately \(3.09 \times 10^{16}\) meters)