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

Example Input: The sun is considered the center of the solar system.
Example Output: What is considered the center of the solar system?

Example Input: A diploid cell is a cell with two chromosomes.
Example Output: What kind of cell is a cell with two chromosomes?

Example Input: After an infection has been brought under control and most cytotoxic t cells die off, a few remain as memory cells.
Example Output:
After an infection has been brought under control and most cytotoxic t cells die off, a few remain as what?