Context: Read the passage. Then answer the question.

A barn swallow preens, or grooms its feathers, by coating them in a thin layer of oil. The oil comes from a small organ near the swallow's tail, called the preen gland. The oil from the preen gland keeps the swallow's feathers strong and flexible.
The oil is also used by a small arachnid called a feather mite. The feather mite lives on the swallow's feathers and eats some of the oil. But, this type of mite does not affect the growth or condition of the swallow's feathers.
Figure: a barn swallow preening.
Which type of relationship is formed when a feather mite lives on a barn swallow's feathers?
A. parasitic
B. mutualistic
C. commensal
From the given choices, select the correct answer and reply with the letter of the chosen option.

C