题干
— Is there a reading room?
— Yes, .
A：there is
B：it is
C：there isn't
D：it isn't
答案(点此获取答案解析）
A
— Is there a reading room?
— Yes, .
A：there is
B：it is
C：there isn't
D：it isn't
表示氧原子， 
表示氢原子．根据此图，试分别从物质组成、分子构成、物质变化的角度各说出一种观点．
