It is early autumn but many birds (left,have left) for warmer countries already. Какой...

Question

It is early autumn but many birds (left,have left) for warmer countries already. Какой ответ правильый,ответы написаны в скобках.

Answer 1

It is early autumn but many birds (left,have left) for warmer countries already. 

Answer 2

left - покидали
have left - покинули
Здесь будет have left.