instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Avian Respiration Birds have evolved a respiratory system that enables them to fly. Flying is a high-energy process and requires a lot of oxygen. Furthermore, many birds fly in high altitudes where the concentration of oxygen in low. How did birds evolve a respiratory system that is so unique? Decades of research by paleontologists have shown that birds evolved from therapods, meat-eating dinosaurs (Figure 39.14). In fact, fossil evidence shows that meat-eating dinosaurs that lived more than 100 million years ago had a similar flow-through respiratory system with lungs and air sacs. Archaeopteryx and Xiaotingia, for example, were flying dinosaurs and are believed to be early precursors of birds. Answer: oxygen
answer:
Birds have evolved a respiratory system that enables them to fly. flying is a high-energy process and requires a lot of this?

question:
Passage: The convection zone surrounds the radiative zone. In the convection zone, hot material from near the Sun's center rises. This material cools at the surface, and then plunges back downward. The material then receives more heat from the radiative zone. Answer: convection zone
answer:
Hot material from near the sun's center rises in which zone?

question:
Passage: Sugars are simple carbohydrates. Molecules of sugar have just a few carbon atoms. The simplest sugar is glucose (C 6 H 12 O 6 ). Glucose is the sugar that the cells of living things use for energy. Plants and some other organisms make glucose in the process of photosynthesis. Living things that cannot make glucose obtain it by consuming plants or these other organisms. Answer: glucose
answer:
What is the sugar that the cells of living things use for energy?