Solution:
Centaur is the only imaginary-creature in the group.

Solution:
All others earn from the customer.

Solution:
All except Gloves are used to cover the head.

Solution:
In all other groups, first and third letters as well as fourth and second letters are alternate.

Solution:
All except Pinna are bones, while pinna is the external part of an ear.

Solution:
All except Small are prepositions, while, Small is used as an adjective.

Solution:
All except Gallon are units for measuring the weights of solids.