single traits

例句：

1. 1.The single most important thing is to have a clear goal.
   最重要的事情是有明确的目标。
2. 2.She has only one friend in the world.
   她世界上只有一个朋友。
3. 3. There are only three stars in the sky tonight.
   今晚天上只有三颗星星。