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

The double helix dna shape forms when the two nucleotide chains wrap around the same axis.
What distinctive dna shape forms when the two nucleotide chains wrap around the same axis?

Water can be boiled to kill giardia and most other pathogens.
Water can be boiled to kill giardia and most other what?

Space efficiency is the major selective advantage of myelination.
What is the major selective advantage of myelination?