My father ____(have) a headache yesterday.
John as well as the other children who ______ no parents ______ good care of in the center.
下图为皮肤的结构,其中结构8是____。皮肤是一种组织、一种器官,还是一个系统?作出判断____,并说说理由____。
下列图例中,通常用于表示铁路的是( )