将下列单词按要求分类，并将其填入相应的类别中。

pencil                hand              purple            duck             blue     

squirrel             eraser              nose           sharpener        rabbit    

yellow              mouth               pig             monkey           arm        

head                  ruler               finger

1. 文具类：                                                                                       

2. 身体部位类：                                                                                

3. 颜色类：                                                                                       

4. 动物类：                                                                                        

颌间挛缩的特点（）

A.临床表现是张口困难

B.外伤和感染所致

C.头颈部大剂量的放射性照射可导致

D.面部有明显的瘢痕，缺损畸形或扪及纤维条索

E.手术治疗为主