Question

a cell membrane is not
a fluid structure.
a rigid structure.
a mosaic structure.
a bilayered structure.
composed of phospholipid molecules.

Explanation:

The fluid mosaic model describes cell membranes as flexible (fluid), bilayered structures made of phospholipids, with embedded proteins creating a mosaic pattern. They are not rigid, as components can move within the membrane.

Answer:

a rigid structure.