Answer:
Answer D
Explanation:
It's not answer A because that is the main goal of the cell membrane.
It's also not answer B because at first glance, you may think that this is the goal of the nuculeus, HOWEVER, this is also the perpous of the cell membrane.
Finally, its not answer C because that is just answer A, but reworded to make it sound different.
The answer is answer D because communicating between cells is the goal of the Endoplasmic Reticulum, aka the ER.