left exact covariant functor

例句：

1. 1. The team left the city early in the morning.
   队伍一大早就离开了城市。
2. 2. He left his homeland to study abroad.
   他离开祖国去国外留学。
3. 3. The train left the station at 7:00 a.m.
   火车在早上7点离开了车站。