A cannot be the answer as living things can reproduce asexually, which is by budding.
C cannot be the answer as we humans who are also living things cannot make our own food.
D cannot be the answer as single-cell organisms such as a plankton do not need an organ system, since all life processes in the organism occur in one cell.
Protoplasm is defined as the organic and inorganic substances that constitute the living the nucleus, cytoplasm, plastids and mitochondria of the cell.