有顺反异构体的化合物是()。
A. 丁-1-烯
B. 丁-2-烯
C. 2-甲基丁-2-烯
D. 戊1,4-二烯
使用be动词提问和回答-Is he a teacher?
A. Yes, he is.
B. No, he is.
C. No, he isn’t.
D. Yes, he isn’t.
使用be动词提问和回答 -Are you a teacher?
A. Yes, I am not.
B. No, I am not.
C. Yes, I am.
D. No, I am.
使用be动词提问和回答 -Were they teachers?
A. Yes, they were.
B. No, they are.
C. No, they weren’t.
D. Yes, they are.