TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: A crater can usually be found on the top of composite volcanoes.

SOLUTION: A crater can usually be found on the top of what kind of volcanoes?

PROBLEM: The values of strangeness assigned to various particles are based on decay systematics.

SOLUTION: The values of strangeness assigned to various particles are based on what?

PROBLEM: Phospholipids are the main component of the cell membrane.

SOLUTION:
What is the main makeup of the cell membrane?