Carbohydrate layer on the plasma membrane gives:
(a) protection
(b) cell recognition
(c) gives a cell its distinctive characteristics
(d) all are correct

All are correct.

Explanation:

The plasma membrane consists of lipid bilayers and proteins are inserted or may span the membrane bilayer. The carbohydrate are always present in the plams membrane in association with lipids and proteins known as glycolipids and glycoproteins.

The carbohydrate layer on plasma membrane acts as the physical barrier and provide protection against the pathogens. The carbohydrate-selectin present on the plasma membrane helps in the cell recognition and makes its distinct from the normal cells. The cell recognition of carbohydrate molecule is important for the embryonic development as well.

Thus, the correct answer is option (d).