Living matter is at least sixty percent water. it makes sense then cell membranes are made of phospholipids because

The non-polar fatty acid tails of amphipathic phospholipids make the insoluble boundary of cells.

Explanation:

Cell membranes are bilayer of phospholipids. Phospholipids are amphipathic molecules and have a polar head and non-polar tail. The non-polar tails of two phospholipid layers are buried and make the core of the membrane while the polar heads are located towards the surrounding water.

This arrangement of phospholipids makes an insoluble covering of cell and helps the cell to maintain the interior distinct from the surroundings.

the answers are a and c