How is the plasma membrane arranged?

Proteins are indeed integral to the plasma membrane, but they do not form the structural layer itself. Instead, the plasma membrane is made primarily of phospholipids, with proteins embedded within or attached to this phospholipid bilayer. Therefore, this choice inaccurately describes the fundamental structure of the membrane.

While the plasma membrane does have a double layer, it is not composed of proteins. The double layer consists of phospholipids, with proteins being present as components that serve various functions, such as transport and signaling. This choice misrepresents the essential building blocks of the membrane.

The plasma membrane is organized as a bilayer of phospholipids, not a single layer. A single layer would not effectively form a barrier to separate the cell's internal and external environments. This choice fails to capture the critical bilayer structure that is vital for membrane integrity and function.