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

Ex Input:
The nuclear envelope is a double-layered plasma membrane like the cell membrane, although without membrane proteins.

Ex Output:
The nuclear envelope is a double-layered plasma membrane like the cell membrane, although without what?


Ex Input:
2 hydrogen, 1 oxygen atoms combine to make up a molecule of water.

Ex Output:
What atoms combine to make up a molecule of water?


Ex Input:
Space efficiency is the major selective advantage of myelination.

Ex Output:

What is the major selective advantage of myelination?