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

[EX Q]: Humans have 23 pairs pairs of chromosomes.
[EX A]: How many pairs of chromosomes do human have ?

[EX Q]: Water can be boiled to kill giardia and most other pathogens.
[EX A]: Water can be boiled to kill giardia and most other what?

[EX Q]: A mold is an imprint of an organism left in rock.
[EX A]:
A mold is an imprint of an organism left in what?