Final answer:
True, the yolk sac produces the first blood cells for the fetus during the early stages of development and is involved in primitive blood circulation.
Step-by-step explanation:
The statement that the yolk sac makes new blood cells for the fetus is True. During the early stages of embryonic development, specifically during the second and third week, the yolk sac does indeed function in producing the first blood cells and provides primitive blood circulation. This role is eventually taken over by other organs as the fetus develops; initially by the spleen, lymph nodes, and liver, and later by the bone marrow which ultimately assumes the hematopoietic functions. Furthermore, the yolk sac is integral to the formation of the umbilical cord structure and contributes to the embryo's early nutrition.