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

Ex Input:
Passage: Cells are the tiny building blocks of living things. They couldn't be discovered until the microscope was invented. The discovery of cells led to the cell theory. This is one of the most important theories in life science. Answer: cells

Ex Output:
What are all living things made of?

Ex Input:
Passage: Over 99 percent of all species that ever lived on Earth have gone extinct. Five mass extinctions are recorded in the fossil record. They were caused by major geologic and climatic events. Evidence shows that a sixth mass extinction is occurring now. Unlike previous mass extinctions, the sixth extinction is due to human actions. Answer: 99%

Ex Output:
What percentage of all species that ever lived on earth have gone extinct?

Ex Input:
Passage: It was known that DNA is composed of nucleotides , each of which contains a nitrogen-containing base, a five-carbon sugar (deoxyribose), and a phosphate group. In these nucleotides, there is one of the four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T) ( Figure below ). Adenine and guanine are purine bases, and cytosine and thymine are pyrimidine bases. Answer: nitrogen

Ex Output:
What does the base of a nucleotide within dna consist of?