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

Input: Consider Input: Passage: Oxygen is needed to make ozone. Ozone is a molecule made of three oxygen ions. Ozone in the upper atmosphere blocks harmful solar radiation from reaching the surface. Without oxygen, life on Earth would have been very simple. Answer: three

Output: How many oxygen ions make up an ozone molecule?

Input: Consider 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

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

Input: Consider Input: Passage: All electric circuits have at least two parts: a voltage source and a conductor. They may have other parts as well, such as light bulbs and switches, as in the simple circuit seen in the Figure below . To see an animation of a circuit like this one, go to: http://www. rkm. com. au/animations/animation-electrical-circuit. html. Answer: electric circuits
Output: A voltage source and a conductor are common to all what?