6. A previously unknown cell type is discovered in the central nervous system of a laboratory strain of mice. In cell-culture experiments, researchers find that the cell type can self-renew, but can only differentiate into one cell type. Which of the following best characterizes this cell type? (2 points)(A)Unipotent embryonic stem cell(B)Unipotent somatic stem cell(C)Multipotent somatic stem cell(D)Multipotent embryonic stem cell