Introduction:
Ascaris lumbricoides is a common intestinal parasite that infects humans. The life cycle of Ascaris involves migration within the human body, including passage through the lungs. During this migration, the larvae travel through specific blood vessels to reach the lungs.

Pulmonary Artery:
The correct answer is option 'D', the pulmonary artery. The reason behind this is the anatomical pathway that the larvae of Ascaris take during their migration through the human body.

Life Cycle of Ascaris:
1. Ingestion: Ascaris eggs are ingested by humans through contaminated food or water.
2. Intestinal Invasion: After ingestion, the eggs hatch in the small intestine, releasing larvae.
3. Migration: The larvae then penetrate the intestinal wall, enter the bloodstream, and migrate to the liver.
4. Hepatic Vein: From the liver, the larvae travel to the heart through the hepatic vein. However, the question specifically asks about the blood vessel that carries the larvae in the lungs, so the hepatic vein is not the correct answer.

The Pulmonary Artery:
5. Pulmonary Artery: Once the larvae reach the heart, they are pumped into the pulmonary artery, which carries deoxygenated blood from the heart to the lungs. The larvae then enter the capillaries of the pulmonary circulation within the lungs. The pulmonary artery is the only blood vessel out of the given options that carries blood to the lungs, making it the correct answer.

Pulmonary Vein:
6. Pulmonary Vein: After spending some time in the lung capillaries, the larvae migrate into the alveoli (air sacs) of the lungs. From there, they enter the bronchi and trachea, eventually reaching the throat and being swallowed. It is important to note that the pulmonary vein carries oxygenated blood from the lungs back to the heart, so it is not the vessel that carries the larvae to the lungs.

Conclusion:
In conclusion, the correct blood vessel that carries the larvae of Ascaris in the lungs is the pulmonary artery. The larvae enter the lungs through the capillaries of the pulmonary circulation, which are supplied by the pulmonary artery. The pulmonary vein carries oxygenated blood from the lungs back to the heart, while the hepatic vein carries blood from the liver to the heart.