Identify , typical dental formula of a metatherian

Options

A. i5/4 , c 1/1 , pm 3/3 , m 4/4
B. i3/3 , 1/1 , pm 4/4 , m 3/3
C. i4/3 , c 1/1 , pm 3/3 , m 4/4
D. i4/5 , c 1/1 , pm 3/3 , m4/4.

Answer

To identify the typical dental formula of a metatherian, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Dental Formula**:
- The dental formula is a way to represent the number and types of teeth in an organism. It is expressed as a fraction, where the upper part represents the teeth in the upper jaw and the lower part represents the teeth in the lower jaw.

2. **Identify Metatherians**:
- Metatherians are a group of mammals that are more closely related to marsupials than to placental mammals. Examples include kangaroos and opossums.

3. **Determine the Number of Teeth in Metatherians**:
- The dental formula for metatherians includes:
- **Incisors**: 5 pairs in the upper jaw and 4 pairs in the lower jaw.
- **Canines**: 1 pair in both the upper and lower jaws.
- **Premolars**: 3 pairs in both the upper and lower jaws.
- **Molars**: 4 pairs in both the upper and lower jaws.

4. **Write the Dental Formula**:
- The dental formula can be expressed as:
- Upper Jaw: 5 incisors, 1 canine, 3 premolars, 4 molars
- Lower Jaw: 4 incisors, 1 canine, 3 premolars, 4 molars
- Therefore, the typical dental formula of a metatherian is written as:
- **5/4, 1/1, 3/3, 4/4**

5. **Verify Against Options**:
- If provided with multiple-choice options, check which one matches the derived dental formula. The correct option should reflect the numbers calculated above.

### Final Answer:
The typical dental formula of a metatherian is **5/4, 1/1, 3/3, 4/4**.