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

Example Input: Passage: Steel is an example of an alloy. An alloy is a mixture of a metal with one or more other elements. The other elements may be metals, nonmetals, or both. An alloy is a solid solution. It is formed by melting a metal and dissolving the other elements in it. The molten solution is then allowed to cool and harden. Several other examples of alloys and their uses are shown in Figure below . You can learn about an amazing alloy called memory wire at the URL below. If you have braces on your teeth, you may even have this alloy in your mouth!. Answer: an alloy
Example Output: A mixture of a metal with one or more other elements is called?

Example Input: Passage: There are three types of mechanical waves. They differ in how they travel through a medium. The three types are transverse, longitudinal, and surface waves. All three types are described in detail below. Answer: three
Example Output: How many types of mechanical waves are there?

Example Input: Passage: Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. Only with fluorine does oxygen form compounds in positive oxidation states. Answer: positive oxidation states
Example Output:
Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. only with fluorine does oxygen form compounds in this?