OG12蓝皮112 求助

112. Inthe 1980s the federal government was the largest single provider of day care for children, offering child care, health , and educational servicesto hundreds of thousands of children from poor households through the Head Start program and which supported private day-care facilities through child-care tax credits, state block grants, and tax breaks for employers who subsidized day-care services.
(A) In the 1980s the federal government was the largest single provider of day care for children , offering
(B) The federal government was the largest single provider of day care for children in the 1980s,which offered
(C) In the 1980sthe federal government was the largest single provider of daycare for children and offered
(D) The largest single provider of day care for children in the 1980swas the federal government, offering
(E) In the 1980sthe largest single provider of day care for children was the federal government, which offered
答案为D，但是我对C和D区别搞不清楚。请教NN指教