The right answer is A.
Adult stem cells are undifferentiated cells found in tissues that are predominantly composed of differentiated cells in most adult tissues and organs. These are usually multipotent cells. They are able to give rise to different cell lines of a given tissue. They are the basis of the natural renewal of a tissue and its repair following an injury.
Unlike the use of embryonic stem cells, those of adult stem cells pose no ethical problem as they are not derived from samples of destroyed human embryos.
DNA is made of chemical building blocks called nucleotides. These building blocks are made of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating.
Answer:
The plasma membrane of a cell is a network of lipids and proteins that forms the boundary between a cell’s contents and the outside of the cell. It is also simply called the cell membrane. The main function of the plasma membrane is to protect the cell from its surrounding environment.