The fluid mosaic model is proposed for the:

Correct answer: (a) Plasma membrane

Explanation

The fluid mosaic model, proposed by S. J. Singer and Garth Nicolson in 1972, describes the structure of the plasma membrane (cell membrane).

The membrane is a lipid bilayer of phospholipids (with cholesterol) in which proteins are embedded or attached, like a mosaic. It is fluid because the lipids and many proteins can move sideways. The membranes of organelles have a similar structure, but the model was made for the plasma membrane.