And although these biofuels will probably first be supplied preblended with traditional gasoline or diesel, one day we may use them alone and say good-bye to petroleum-based gasoline forever.

当然，刚开始的时候，这类生物燃料还是只能与传统的汽油或柴油混合使用，但迟早都有能够单独使用的一天。 到了那一天，我们就可以永远告别利用石油来提炼汽油的时代。

youdao

After the movie was finished, James said good-bye to his friends and walked home alone.

电影结束后，詹姆斯跟朋友道别，然后独自走回家。

youdao

Police probing Finland's first known school shooting said Thursday that a picture was emerging of the gunman as a lonely, antisocial 18-year-old who acted alone and left a suicide note saying good-bye to his family, but that his motive was unclear.

CNN: Finland in mourning after fatal school shooting