找出下列单词不同类的一项。
⑴A. dad        B. mother     C. girl       D. sister
⑵A. China      B. UK         C. USA        D. Beijing
⑶A. tail       B. fat        C. tall       D. thin
⑷A. in         B. big        C. on         D, under
⑸A. thirteen    B. fourteen    C. fifteen     D. pupil