Concept:The cytoplasmic membrane, also called the cell membrane or plasma membrane, is the outer boundary that regulates what enters and leaves the cell.
Explanation:The cell is surrounded by a selectively permeable membrane.
This membrane controls the movement of substances in and out of the cell.
It allows useful materials like water, oxygen, and nutrients to enter.
It also allows waste products to leave the cell.
The term "cytoplasmic membrane" is another name for this same cell membrane.
The nuclear membrane only controls the nucleus, while protoplasm and endoplasm are not outer boundary structures.
Answer:A. cytoplasmic membrane.