相差显微镜与普通光学显微镜的区别是用（）代替可变光阑，用（）代替普通物镜，并带有一个合轴用的望远镜。
参考答案：环状光阑；带相差板的物镜
The English play _____ my classmates acted at the get-together was really a great success. [ ]
A. for which
B. at which
C. in which
D. on which
环境水利学的基本内容有哪些？
