题目

The book was written in 1946, ___ the education system has witnessed great changes. A . when B . during which C . since then D . since when 答案：D温带森林中，在大陆东、西部都有分布，且具有不同气候特点的自然带是 A.亚热带常绿硬叶林带    B.亚热带常绿阔叶林带 C.温带落叶阔叶林带      D.亚寒带针叶林带