问题描述：
一道高一英语语法填空怎么写?
Horses,at first,wewe all wild animals loke zebras are today.______ they first evolved in North,by the time people were spreading throughout the world,horses had become xtinct in North America.
Horses,at first,wewe all wild animals loke zebras are today.______ they first evolved in North,by the time people were spreading throughout the world,horses had become xtinct in North America.
问题解答：
我来补答展开全文阅读