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】[解析] improved是improve的过去分词，在句中起形容词作用，“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。