①苯不能使酸性KMnO₄溶液褪色

②苯分子中碳碳键的长度完全相等

③苯能在加热和催化剂存在的条件下与氢气发生反应生成环己烷( )

④经实验测得对二甲苯( )只有一种结构

⑤苯在溴化铁作催化剂条件下同液溴可发生取代反应，但不能因化学反应而使溴水褪色

实验室用稀硫酸除去一定质量的铜粉中混有的铁粉，共消耗稀硫酸50g，生成0.2g氢气．计算稀硫酸中溶质的质量分数．

A:Maria,____?

B:I think a good friend is good at sports.

A:You mean he or she is athletic?

B:Yes.And ____.He or she often makes me laugh.

A:Anything else?

B:Er,I think____ .

A:I can't agree with you. I like to have friends____.

B:Do you think a good friend should be popular in school, too?

A:Well,____.

A. who are different from me

B. how are you

C. a good friend likes to do the same things as me

D. that's not very important for me

E. what is a good friend like

F. you are right

G. he or she is funny

下列句子中划线的词语使用不恰当的一项是（    ）

数3.949×10⁵精确到万位约（　　）