题目

—Is your uncle in his _________?         — Yes. His _________ birthday is coming next month. A. forty; forty-first              B. forties; forty-first     C. forties; forty-one             D. forty; forty-first 答案：B下列所示操作中错误的是（　　）A．    闻气味B．     检查气密性C．     收集氧气D．   稀释浓硫酸