是用a不用an,因为song是以辅音开头，中文意思是n. 歌，歌曲；歌唱，声乐；（鸟的）鸣啭，啼啭；押韵的诗歌
She lip-synced to a Beatles song.她对口形假唱一首披头士乐队的歌曲。
I wrote this sappy love song.我写了这首愚蠢的爱情歌曲。
A song just does things to me.
