读短文，填空

    Hello ! My name is Amy .I'm a girl .I'm from England. Look !This is my father and this is my mother .My father is a teacher. My mother is a doctor .The boy is my brother .He's eight .He's a student .who's this girl ? Can you guess??

血细胞包括____、____ 和____。血液分层后，____在下层，呈红色，

____和____在两层的交界处，很薄，呈白色。