Arrange the following in descending order of their size.

Options

A. `DNA rarr tRNA rarr mRNA rarr rRNA`
B. `DNA rarr mRNA rarr rRNA rarr tRNA`
C. `DNA rarr rRNA rarr mRNA rarr tRNA`
D. `DNA rarr rRNA rarr tRNA rarr mRNA`

Answer

To arrange the given biological molecules in descending order of their size, we will analyze the sizes of DNA, mRNA, rRNA, and tRNA based on the information provided.

### Step-by-Step Solution:

1. **Identify the Sizes of Each Molecule:**
- **DNA:** Approximately 2.3 meters (or 2300 millimeters).
- **mRNA:** Approximately 300 nanometers (or 0.3 micrometers).
- **rRNA:** Approximately 50 nanometers (or 0.05 micrometers).
- **tRNA:** Approximately 20 nanometers (or 0.02 micrometers).

2. **Convert All Sizes to the Same Unit for Comparison:**
- Convert DNA size from meters to nanometers:
- 1 meter = 1,000,000,000 nanometers
- Therefore, 2.3 meters = 2.3 x 1,000,000,000 = 2,300,000,000 nanometers.
- mRNA = 300 nanometers.
- rRNA = 50 nanometers.
- tRNA = 20 nanometers.

3. **Arrange the Sizes in Descending Order:**
- Start with the largest size:
- **DNA:** 2,300,000,000 nanometers
- **mRNA:** 300 nanometers
- **rRNA:** 50 nanometers
- **tRNA:** 20 nanometers

4. **Final Arrangement:**
- The descending order of size is:
- **DNA > mRNA > rRNA > tRNA**

### Conclusion:
The correct order of the biological molecules from largest to smallest is:
1. DNA
2. mRNA
3. rRNA
4. tRNA