A:e2013f(-2013)<f(0),f(2013)>e2013f(0)
B:e2013f(-2013)<f(0),f(2013)<e2013f(0)
C:e2013f(-2013)>f(0),f(2013)>e2013f(0)
D:e2013f(-2013)>f(0),f(2013)<e2013f(0)
CuO和Cu(OH)2固体混合粉末20g,其中铜元素的质量分数为72%,放入一定量的稀硫酸中,恰好与两种固体完全反应,反应后形成溶液的溶质质量分数为18%,则加入稀硫酸的溶质质量分数为( )
A:Hey,Rita!What is your new school like?
B:It's big and nice.
A:____
B:Yes,it does.
B:We must get to school before 8:00 a.m.We can't eat in the classroom.
B:Yes.we do.
B:No,we can't.
B:Very good.I think they're good for us.
A:Do you have fun at your new school?
B:Yeah!
A.Can you wear your hats in class?
B.Does it have many rules?
C.What canyoudo?
D.What are the rules?
E.Can I help you?
F.Do you have to wear your uniforms at school?
G.What do you think of these rules?
空气是一种宝贵的自然资源,下列气体不可直接从空气分离获得的是( )