Answer:
The correct answer would be the pulmonary vein and the superior vena cava.
Pulmonary vein is a blood vessel of pulmonary circulation which carries oxygenated blood from lungs to the left atrium of the heart. Hence, it is rich in oxygen and carries carbon dioxide in the least amount.
In contrast, vena cava is a part of systemic circulation and carries deoxygenated blood from the body to the right atrium of the heart. They are two venae cavae in human beings namely; inferior vena cava (carries blood from lower body) and superior vena cava (carries blood from head, arms and upper body). Hence, it contains maximum carbon dioxide and least oxygen.
Fertile land is lost, and there is increased pollution and sedimentation in rivers and other aquatic areas.
Because a spring is from where the water table is too high
E. coli bacteria would not have a well defined nucleus, because bacteria are prokaryotic cells.
The onion cell and the human brain cell would be eukaryotic cells, which do have nuclei.