A. Okay
B. I'm sick
C. What's the matter
Mom:Are you okay?
Mike:No, ____.
Mom:Let's see a doctor.
Mike: ____!
Doctor: ____?
Mike:My head hurts.
实验
①
②
③
电解条件
阴、阳极均
为石墨
阴、阳极均为石墨,滴
加1mL浓硫酸
阴极为石墨,阳极为铁,
滴加1mL浓硫酸
Cr2O72-的去除率/%
0.922
12.7
57.3
列举宋元时期发明并广泛使用的三项重大科技成就。
Tom p____ to die rather than give in when he was arrested.
如图是某个生物兴趣小组对一个农田生态系统做调查之后,所绘制的食物网简图,请据图回答问题: