Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Input: Consider Input: The newest, outer layers of secondary xylem are called sapwood.

Output: What are the newest, outer layers of secondary xylem called?


Input: Consider Input: Healthy lungs is necessary in a person who wishes to play wind instruments.

Output: What is necessary in a person who wishes to play wind instruments?


Input: Consider Input: Coal can be mined from earth and used as an energy source.
Output: Which of these can be mined from Earth and used as an energy source?