再问ets出版物里面的一道语法题

sureho

Bacause of their highly developed sense of hearing, dolphins are able to hear a wide range of low and high-pitched sounds, including many that cannot be detected by human.

答案d, 不明?难道要改成human beings?

wakim

直接humans好像也可吧，对应一下，前面都是dolphins

n9ga1

都可以的

david_he

human是可数名词，必须加a,the,or改成复数。