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.
A. an easy B. a playful C. an open D. a better

【正确答案】 D
【答案解析】improved：improve的过去分词，在句中起形容词的作用，即修饰learning environment，表示“改进了的；更好的”，与better意思相近。easy：容易的。playful：顽皮的；闹着玩的。 open：公开的；开着的。