Context: Read the passage. Then answer the question.

Julia butterflies get most of their nutrients by eating nectar from flowers. But a Julia butterfly cannot get enough salt from nectar to survive. The butterfly finds some of the salt it needs in the tears of a reptile called a spectacled caiman.
To get the salt, the butterfly lands on a caiman's head and uses its straw-like mouthparts to drink tears directly from the caiman's eye! The caiman is not helped or harmed by the butterfly. While the butterfly drinks, the caiman often does not move or even blink.
Figure: a Julia butterfly drinking a spectacled caiman's tears.
Which type of relationship is formed when a Julia butterfly drinks a spectacled caiman's tears?
A. mutualistic
B. parasitic
C. commensal
Answer with the option's letter from the given choices directly.

C