单选题 Although originally a German innovation, kindergarten got its real start in the United States as a movement to provide an improved learning environment for children.
【正确答案】 D
【答案解析】[解析] improve：改进，提高，而improve+ed变成过去分词也可以作定语，那么就含有被动的意思，即“被改进的”，也就是“更好的”。