Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: Pulmonary circulation is the part of the circulatory system that carries blood between the heart and lungs (the term pulmonary means "of the lungs"). It is illustrated in Figure below . Deoxygenated blood leaves the right ventricle through pulmonary arteries, which transport it to the lungs. In the lungs, the blood gives up carbon dioxide and picks up oxygen. The oxygenated blood then returns to the left atrium of the heart through pulmonary veins. Answer: oxygen

Ex Output:
While in the lungs, blood gives up carbon dioxide and picks up what element before returning to the heart?

Ex Input:
Passage: Bacteria can be used to make cheese from milk. The bacteria turn the milk sugars into lactic acid. The acid is what causes the milk to curdle to form cheese. Bacteria are also involved in producing other foods. Yogurt is made by using bacteria to ferment milk ( Figure below ). Fermenting cabbage with bacteria produces sauerkraut. Answer: lactic acid

Ex Output:
Bacteria can be used to make cheese from milk. the bacteria turn the milk sugars into what?

Ex Input:
Passage: An example of a mutualistic relationship is between herbivores (plant-eaters) and the bacteria that live in their intestines. The bacteria get a place to live. Meanwhile, the bacteria help the herbivore digest food. Both species benefit, so this is a mutualistic relationship. The clownfish and the sea anemones also have a mutualistic relationship. The clownfish protects the anemone from anemone-eating fish, and the stinging tentacles of the anemone protect the clownfish from predators ( Figure below ). Another example of this type of symbiotic relationship is the relationship between the plover bird and the African crocodile. The tiny blackbird acts as a toothpick for the fierce crocodile, and helps by removing tiny morsels of food that are stuck between the crocodile's teeth. These food remains are the source of food for the bird. Another example is between the ostrich and the zebra. The ostrich always moves with the herd of zebras since it has a poor sense of hearing and smell, whereas the zebra has very sharp senses. The ostrich has a keen sense of sight, which the zebra lacks. Hence, these two species depend on each other to warn one another of any nearby imposing dangers. Answer: mutualism

Ex Output:
Herbivores and the bacteria that live in their intestines demonstrate a two-way beneficial relationship called what?