选择括号中所给词的正确形式填空。

He can't walk because he has not ______ (foot, feet)

根据文段意思，选括号中适当的词填空。

Have you ever seen a horse with toes(脚趾)? Many years ago , horses had many ________( toe , toes ). They had four toes on each front ________( foot , feet ). 'They had three toes on each back foot . The horses were ________( small , smaller)than cats . These small horses lived in the forest(森林). Their many toes helped the horses ________( run , running )over the soft(柔软的)wet(湿的)ground . It was very hot in the forest . But the weather changed . It became cold . Many trees couldn't ________(live, lived)in cold weather. 'The trees died and ________(fall, fell). Open field(土地)took the place of(代替)forests . The sun made the ground dry(干的)and hard(硬的). Horses began ________( change , to change )too . They began to get ________(big, bigger). This took a long time. On the dry hard land(陆地), horses needed only their middle toes for ________(run, running). ________(They, Their)middle toes became hard . After a long time horses had only one hard toe on each foot . We call this hard toe a hoof(马蹄).