Until now I have always lived alone.

　　直到現(xiàn)在，我一直獨(dú)自生活。

　　Pedro walked along the street alone.

　　佩德羅獨(dú)自一人沿著這條街走。

　　The assassin said he had acted alone.

　　暗殺者聲稱(chēng)他是單獨(dú)作案。