A．中子数为6的碳原子612C
B．次氯酸的电子式
C．硫离子结构示意图
D．CH4O的结构式
答案：D
— Hi! Tony, I didn't see you at 8:00 p.m. at the party.
— Oh, I _____ for the coming exam. [ ]
A. studied
B. was studying
C. am studying
辅助视图常见的有剖视图、斜视图和旋转视图。（）
