题干
Who's that man? ________.( )
A：She is my mother.
B：He is my father.
C：This is a book.
答案(点此获取答案解析）
B
Who's that man? ________.( )
A：She is my mother.
B：He is my father.
C：This is a book.
和 
分别表示两种不同元素的原子，那么其中表示混合物（ ）