妹妹单词怎么写

　　例句：

　　His sense of guilt had its roots in his childhood loss of his younger sister

　　他的负疚感源于他在童年失去了妹妹。

　　She and her younger sister are very close.

　　她和她妹妹很亲。

　　I often dreamt of my younger sister soon after I left home.

　　刚离开家时，我常梦见妹妹。

　　But your Size M is so small that I have to give it to my younger sister.

　　但是你的M码太小了,我只好把它给我妹妹。