human什么时候用复数

　　The cost in terms of human life was high.

　　付出了很大的生命代价。

　　Contact with other people is a basic human need.

　　和他人接触是人的基本需要。

　　He's really very human when you get to know him.

　　你若了解他，就知道他确实很有人情味。