**Core Concept**
The Tobey-Ayer test and Croue-Beck test are diagnostic procedures used to assess the patency of the Eustachian tube. The Eustachian tube connects the middle ear to the nasopharynx, playing a crucial role in equalizing middle ear pressure and draining mucus. Abnormalities in the Eustachian tube function can lead to middle ear effusions and hearing loss.

**Why the Correct Answer is Right**
The Tobey-Ayer test and Croue-Beck test are used to assess the patency of the Eustachian tube by observing the movement of the tympanic membrane during swallowing, blowing, or other maneuvers. The tests rely on the principle that the Eustachian tube opens during swallowing, allowing air to enter the middle ear and causing the tympanic membrane to move. The Tobey-Ayer test involves observing the movement of the tympanic membrane during swallowing, while the Croue-Beck test uses a pneumatic otoscope to observe the movement of the tympanic membrane while the patient blows air through the nose.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the diagnostic tests used for Eustachian tube patency.
**Option B:** This option is incorrect because it refers to a different diagnostic test for middle ear function.
**Option C:** This option is incorrect because it is not a recognized diagnostic test for Eustachian tube patency.

**Clinical Pearl / High-Yield Fact**
The Eustachian tube plays a crucial role in maintaining middle ear pressure and drainage of mucus. Abnormalities in Eustachian tube function can lead to middle ear effusions, hearing loss, and other complications.

**Correct Answer: C. Tobey-Ayer test and Croue-Beck test are used for assessing the patency of the Eustachian tube.**