left exact functor

例句：

1. 1. I left my keys on the table when I went to the bathroom.
   我去洗手间时把钥匙落在了桌子上。
2. 2. The car was left in the middle of the road.
   那辆车停在了马路中间。
3. 3. She left the party early because she had a headache.
   她提前离开了派对，因为她头疼。