text: <unk> s are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Research in the<unk>  field grew out of findings by Canadian<unk> ientists Ernest A. McCulloch and James E. Till in the 1960s.
  The two broad types of mammalian<unk> s are: embryonic<unk> s that are found in blastocysts, and adult<unk> s that are found in adult tissues. In a developing embryo,<unk> s can differentiate into all of the specialized embryonic tissues. In adult organisms,<unk> s and progenitor cells act as a repair system for the body, replenishing specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.
  As<unk> s can be grown and transformed into specialized cells with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture, their use in medical therapies has been proposed. In particular, embryonic cell lines, autologous embryonic<unk> s generated through therapeutic cloning, and highly plastic adult<unk> s from the umbilical cord blood or bone marrow are touted as promising candidates.
option_0: Stem cell
option_1: Cell 
option_2: Blood cell
option_3: Hematopoietic stem cell
option_4: Cancer Cell
option_5: Lymphoblast
option_6: Immunoblast
option_7: Cancer stem cell