There are many different proteins found in or on the plasma membrane:
• Integral or transmembrane proteins, such as ion channels or proton pumps
,
• Lipid anchored proteins, for example, G proteins.
,
• Peripheral proteins, that react temporarily with the membrane, such as enzymes and hormones.
They perform several functions, such as recognizing substances on the membrane surface (A), movement of substances across the membrane (B), cell-cell communication (C), among others. This means D is the right answer, all the processes mentioned are carried by membrane proteins.