Final answer:
Improper usage of a wax loop can cause internal feedback in an ITE aid.
Step-by-step explanation:
Internal feedback in an ITE aid can be caused by improper usage of a wax loop. When a wax loop is not properly inserted into the ear, it can cause feedback or a whistling sound. The wax loop is designed to prevent sound from leaking out of the ear and being amplified again by the hearing aid, but if it is not positioned correctly, it can cause internal feedback.
This is different from external feedback, which can be caused by external factors like a toothpick plugging the receiver tube or a dead battery. These external factors can also disrupt the functioning of the hearing aid, but they do not directly cause internal feedback.
So, the correct answer is B. improper usage of a wax loop.