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

Ex Input:
Passage: Bacteria lack many of the structures that eukaryotic cells contain. For example, they don't have a nucleus. They also lack membrane-bound organelles, such as mitochondria or chloroplasts. The DNA of a bacterial cell is also different from a eukaryotic cell. Bacterial DNA is contained in one circular chromosome, located in the cytoplasm. Eukaryotes have several linear chromosomes. Bacteria also have two additional unique features: a cell wall and flagella. Some bacteria also have a capsule outside the cell wall. Answer: one circular chromosome

Ex Output:
How many chromosomes do bacterial dna have?

Ex Input:
Passage: The lungs of mammals are unique in having alveoli. These are tiny, sac-like structures. Each alveolus is surrounded by a network of very small blood vessels (see Figure below ). Because there are millions of alveoli in each lung, they greatly increase the surface area for gas exchange between the lungs and bloodstream. Human lungs, for example, contain about 300 million alveoli. They give the lungs a total surface area for gas exchange of up to 90 square meters (968 square feet). That's about as much surface area as one side of a volleyball court!. Answer: alveoli

Ex Output:
What in mammalian lungs, increases the surface area for gas exchange?

Ex Input:
Passage: The brain and spinal cord make up the central nervous system. Answer: central nervous system

Ex Output:
The brain and spinal cord are part of what system?