Answer:
d. the pattern of proteins on the cell's surface
Step-by-step explanation:
Cell to cell interaction is a very important phenomenon for a multicellular organism where the cells have to coordinate and cooperate to perform similar functions.
The cell interacts with another cell through chemicals which could act as signals to another cell.
The cell to cell interaction depends on the recognition of another cell which is mediated by the proteins. The proteins are present on the cell membrane in the form of receptors and recognition proteins which could be arranged in the pattern. It is the pattern of the proteins which define the specificity to the recognition of the cell.
Thus, option-D is the correct answer.