Correct Answer: Grass

Solution : Let's check each option –
First option: Wool; Wool is obtained from sheep.
Second option: Feather; Feather is obtained from birds.
Third option: Hair; Hair is obtained from animals or birds.
Fourth option: Grass; Grass is obtained from plants.

So, the fourth option does not belong to the group as all the other things are obtained from animals or birds. Hence, the fourth option is correct.