1、第一个单词pencil的复数形式是可以直接加s的变成pencils。
2、第二个单词box要注意应该加es变成boxes，因为box是x结尾，所以要加es例如还有bus→buses，watch→watches
3、下面为同学补充几点：以y结尾的,要改y为i再加es；以f或fe结尾的,要把f或fe改成v, 再加es；只有13个，下面列出：knife-幻腾寂埒-kniveswife--wivesthief--thievesleaf--leaveshalf--halveslife--livesscarf--scarveswolf--wolvesself--selvesyourself--yourselvesmyself--ourselveshimself/herself/itself--themselvesbookshelf--bookselvesdwarf--dwarveshandkerchief--handkerchieves而man,woman,child,mouse等单词是特殊单词。