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

Phospholipids are the main component of the cell membrane.
What is the main makeup of the cell membrane?

Plasma matter makes up most of the universe.
What type of matter makes up most of the universe?

Scientists know that some mountains were once at the bottom of an ocean because marine fossils have been found on the peaks of some mountains.

How do scientists know that some mountains were once at the bottom of an ocean?