In mammalian embryo the pulmonary aorta communicates with carotico-systemic aorta by a narrow ductus arteriosus, in the adult this connection closes learving `:-`

Options

A. Carotico-pulmonary aperture
B. ligamentum arteriosus
C. fossa ovalis
D. none of the above

Answer

To solve the question regarding the closure of the ductus arteriosus in the adult mammal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Ductus Arteriosus**:
- In a mammalian embryo, the ductus arteriosus is a vital blood vessel that connects the pulmonary artery to the aorta. This connection allows blood to bypass the non-functioning lungs, which are filled with fluid during fetal development.

2. **Function During Fetal Development**:
- The ductus arteriosus allows most of the blood from the right ventricle to flow directly into the aorta, thus avoiding the lungs. This is crucial because the fetus does not breathe air and does not require pulmonary circulation.

3. **Closure at Birth**:
- After birth, when the newborn takes its first breath, the lungs expand and the blood flow to the lungs increases. This change in pressure causes the ductus arteriosus to close.

4. **Transformation into Ligamentum Arteriosum**:
- Once the ductus arteriosus closes, it eventually becomes a fibrous remnant known as the ligamentum arteriosum. This is the structure that remains in adults.

5. **Final Answer**:
- Therefore, the connection that closes after birth, leaving a remnant, is known as the **ligamentum arteriosum**.

### Conclusion:
The correct answer to the question is **ligamentum arteriosum**.

---